• 대한전자공학회논문지
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• 제17권3호
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• pp.20-25
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• 1980

Singular value decomposition을 통한 pseudo-inverse를 단층영상 재구성에 이용하였다. 본 논문에서는 SVD pseudo-inverse를 이용한 truncated inverse filter와 Scalar Wiener filter에 대하여 검토하고 각각에 대하여 통계적 측면에서의 최적화가 연구되었다. 이러한 방법은 신호와 잡음문에 trade-off를 기함으로써 재구성 문제에 항상 뒤따르는 ill-conditioning 현상을 극복할 수 있다. 본 논문을 통하여 구성된 filter의 성능을 확인하기 위하여 컴퓨터를 이용한 simulation이 이루어졌으며 그 결과 재구성된 협상은 만족할 만 하였다.

• 한국자기공명학회논문지
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• 제4권2호
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• pp.116-124
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• 2000

Singular value decomposition (SVD) has been used during past few decades in the advanced NMR data processing and in many applicable areas. A new modified SVD, piecewise polynomial truncated SVD (PPTSVD) was developed far the large solvent peak suppression and noise elimination in U signal processing. PPTSVD consists of two algorithms of truncated SVD (TSVD) and L$_1$ problems. In TSVD, some unwanted large solvent peaks and noises are suppressed with a certain son threshold value while signal and noise in raw data are resolved and eliminated out in L$_1$ problem routine. The advantage of the current PPTSVD method compared to many SVD methods is to give the better S/N ratio in spectrum, and less time consuming job that can be applicable to multidimensional NMR data processing.

• Bulletin of the Korean Chemical Society
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• 제24권7호
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• pp.967-970
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• 2003

A new modified singular value decomposition method, piecewise polynomial truncated SVD (PPTSVD), which was originally developed to identify discontinuity of the earth's radial density function, has been used for large solvent peak suppression and noise elimination in nuclear magnetic resonance (NMR) signal processing. PPTSVD consists of two algorithms of truncated SVD (TSVD) and L₁ problems. In TSVD, some unwanted large solvent peaks and noise are suppressed with a certain soft threshold value, whereas signal and noise in raw data are resolved and eliminated in L₁ problems. These two algorithms were systematically programmed to produce high quality of NMR spectra, including a better solvent peak suppression with good spectral line shapes and better noise suppression with a higher signal to noise ratio value up to 27% spectral enhancement, which is applicable to multidimensional NMR data processing.

• 전자공학회논문지
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• 제54권4호
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• pp.91-98
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• 2017

전기 임피던스 단층촬영 기법은 도메인의 표면에 부착된 전극들을 통해 주입된 전류와 측정된 전압 데이터를 기반으로, 미지의 도전율 분포를 복원하는 비파괴 기술이다. 이 논문에서는 전기 임피던스 단층촬영법에서 일반적 Tikhonov 조정을 갖는 역문제를 풀고 도전율 분포를 복원하기 위해 절단된 특이값 분해 기반의 역문제 해법을 제안하였다. 역문제 계산시간을 줄이기 위해 일반 조정행렬을 역행렬 항목에서 분리시키고 절단된 특이값 분해 방법을 적용하였다. 제안한 방법의 성능을 검증하기 위해 모의실험과 팬텀실험을 수행하고 복원결과를 비교하였다.

• 대한의용생체공학회:의공학회지
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• 제24권5호
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• pp.459-464
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• 2003

심자도 신호로부터 전류원의 분포를 복원하는 알고리듬을 구성하고 이를 WPW 증후군 환자에 대해 적용하여 임상적 유용성을 검토하였다. 40 채널 superconducting quantum interference device (SQUID) 미분계를 이용하여 심자도를 측정하고 minimum norm estimation (MNE) 알고리듬과 truncated singular value decomposition (SVD)을 적용하여 2 차원 평면에서의 전류원 분포를 구하였으며. 전류원의 분포가 실제 전류원의 정보를 잘 반영하고 있음을 시뮬레이션으로 확인하였다. 또한 좌심방과 좌심실 사이에 부전도로를 가진 WPW 증후군 환자의 심자도를 측정하여 수술 전후의 전류원 분포를 비교한 결과 수술 전에는 부전도로를 통한 비정상전류의 흐름을 볼 수 있었으나 부전도로를 절제한 후에는 더 이상 볼 수 없었다. 이 결과는 심자도 선호로부터 구한 전류원 분포가 심장의 전기 활동을 잘 반영하고 있으며 임상적으로 유용하게 활용 될 수 있음을 보여준다.

• Structural Engineering and Mechanics
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• 제63권6호
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• pp.743-750
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• 2017

Modal parameter identification plays a key role in the structural health monitoring (SHM) for civil engineering. Eigensystem realization algorithm (ERA) is one of the most popular identification methods. However, the complex environment around civil structures can introduce the noises into the measurement from SHM system. The spurious modes would be generated due to the noises during ERA process, which are usually ignored and be recognized as physical modes. This paper proposes an improved stabilization diagram method in ERA to distinguish the spurious modes. First, it is proved that the ERA can be performed by any two Hankel matrices with one time step shift. The effect of noises on the eigenvalues of structure is illustrated when the choice of two Hankel matrices with one time step shift is different. Then, a moving data diagram is proposed to combine the traditional stabilization diagram to form the improved stabilization diagram method. The moving data diagram shows the mode variation along the different choice of Hankel matrices, which indicates whether the mode is spurious or not. The traditional stabilization diagram helps to determine the concerned truncated order before moving data diagram is implemented. Finally, the proposed method is proved through a numerical example. The results show that the proposed method can distinguish the spurious modes.

• Structural Engineering and Mechanics
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• 제27권5호
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• pp.625-638
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• 2007

The damage detection process may appear difficult to be implemented for truss structures because not all degrees of freedom in the numerical model can be experimentally measured. In this context, the damage locating vector (DLV) method, introduced by Bernal (2002), is a useful approach because it is effective when operating with an arbitrary number of sensors, a truncated modal basis and multiple damage scenarios, while keeping the calculation in a low level. In addition, the present paper also evaluates the noise influence on the accuracy of the DLV method. In order to verify the DLV behavior under different damages intensities and, mainly, in presence of measurement noise, a parametric study had been carried out. Different excitations as well as damage scenarios are numerically tested in a continuous Warren truss structure subjected to five noise levels with a set of limited measurement sensors. Besides this, it is proposed another way to determine the damage locating vectors in the DLV procedure. The idea is to contribute with an alternative option to solve the problem with a more widespread algebraic method. The original formulation via singular value decomposition (SVD) is replaced by a common solution of an eigenvector-eigenvalue problem. The final results show that the DLV method, enhanced with the alternative solution proposed in this paper, was able to correctly locate the damaged bars, using an output-only system identification procedure, even considering small intensities of damage and moderate noise levels.