• 대한전자공학회논문지
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• 제26권10호
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• pp.1507-1517
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• 1989

Singular values and their gradients have been used to analyze the stability and sensitivity of continuous multiloop systems. But this method has been limited to the discrete systems. This method is extended in this paper to analyze discrete systems directly in discrete domain. To do this, derived is the relationship in the disrete system between the stability margins and the minimum singular value of the return differene matrix, and also implemented is a method which computes singular value gradients. This method is applied to the lateralattitude control loop of a remotely piloted vehide both in continuous case and discrete case for verification of its utility.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.51-52
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• 2011

본 논문에서는 WT(Wavelet Transform)와 SVD(Singular Value Decomposition)기법을 결합한 WSVD(Wavelet Singular Value Decomposition)를 사용하여, 송전계통에서 부하 탈락 시 나타나는 특성 및 외란검출의 유효성을 분석하였다. WSVD 방식을 이용한 외란검출을 모의하기 위해 EMTP-RV를 이용하여 부산 및 경남 일부지역 345kV급 송전계통을 모델링하였고, 이 계통에서 부하 탈락을 모의하였다. WSVD의 계산은 MATLAB을 통해 수행하였으며, 이 결과를 바탕으로 전력계통에서 부하 탈략량의 변화에 따른 특징을 분석하였다

• Steel and Composite Structures
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• 제51권6호
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• pp.713-727
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• 2024

Damage detection in structures using the change of modal parameters (modal shapes and natural frequencies) has achieved satisfactory results. However, as modal shapes and natural frequencies alone may not provide enough information to accurately detect damages. Therefore, a hybrid singular value decomposition and deep belief network approach is developed to effectively identify damages in aluminum plate structures. Firstly, damage locations are determined using singular value decomposition (SVD) to reveal the singularities of measured displacement modal shapes. Secondly, using experimental modal analysis (EMA) to measure the natural frequencies of damaged aluminum plates as inputs, deep belief network (DBN) is employed to search damage severities from the damage evaluation database, which are calculated using finite element method (FEM). Both simulations and experimental investigations are performed to evaluate the performance of the presented hybrid method. Several damage cases in a simply supported aluminum plate show that the presented method is effective to identify multiple damages in aluminum plates with reasonable precision.

• 대한방사선기술학회지:방사선기술과학
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• 제42권2호
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• pp.119-130
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• 2019

Positron emission tomography (PET) is widely used imaging modality for effective and accurate functional testing and medical diagnosis using radioactive isotopes. However, PET has difficulties in acquiring images with high image quality due to constraints such as the amount of radioactive isotopes injected into the patient, the detection time, the characteristics of the detector, and the patient's motion. In order to overcome this problem, we have succeeded to improve the image quality by using the dynamic image reconstruction method based on singular value decomposition. However, there is still some question about the characteristics of the proposed technique. In this study, the characteristics of reconstruction method based on singular value decomposition was estimated over computational simulation. As a result, we confirmed that the singular value decomposition based reconstruction technique distinguishes the images well when the signal - to - noise ratio of the input image is more than 20 decibels and the feature vector angle is more than 60 degrees. In addition, the proposed methode to estimate the characteristics of reconstruction technique can be applied to other spatio-temporal feature based dynamic image reconstruction techniques. The deduced conclusion of this study can be useful guideline to apply medical image into SVD based dynamic image reconstruction technique to improve the accuracy of medical diagnosis.

• ETRI Journal
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• 제40권5호
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• pp.634-642
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• 2018

Projection spectral analysis is investigated and refined in this paper, in order to unify principal component analysis and independent component analysis. Singular value decomposition and spectral theorems are applied to nonsymmetric correlation or covariance matrices with multiplicities or singularities, where projections and nilpotents are obtained. Therefore, the suggested approach not only utilizes a sum-product of orthogonal projection operators and real distinct eigenvalues for squared singular values, but also reduces the dimension of correlation or covariance if there are multiple zero eigenvalues. Moreover, incremental learning strategies of projection spectral analysis are also suggested to improve the performance.

• ETRI Journal
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• 제45권4호
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• pp.704-712
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• 2023

This paper presents a flexible finite-difference technique for analyzing the nonuniform guiding structures. Because the voltage and current variations along the nonuniform structure differ for each segment, this work considers the adaptable discretization steps. This technique increases the accuracy of the final response. Moreover, by applying the singular value decomposition and discarding the nonprincipal singular values, an optimal lower rank approximation of the discretization matrix is obtained. The computational cost of the introduced method is significantly reduced using the optimal discretization matrix. Also, the proposed method can be extended to the nonuniform waveguides. The technique is verified by analyzing several practical transmission lines and waveguides with nonuniform profiles.

• 소음진동
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• 제9권1호
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• pp.163-173
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• 1999

Precise and reasonable modelling is necessary and indispensable to the analysis of dynamic characteristics of mechanical structures. Also. the effective prediction of the change of modal properties due to the variation of design parameters is required especially for the application of finite element method to the structural dynamics problems. To meet those necessity and requirement, three model updating algorithms are proposed for finite element methods. Those algorithms are based on sensitivity analysis of the modal data obtained from experimental modal analysis(EMA) and analytical modal analysis(AMA). The adapted sensitivity analysis methods of the algorithms are 1)eigensensitivity(EGNS) method. 2)frequency response function sensitivity(FRFS) method. 3)sensitivity based element-by-element method (SBEEM), Singular value decomposition(SVD) is used for performing eigenanalysis and parameter estimation in the updating process. Those algorithms are applied to finite element of a plate and the updating capability of each algorithm is compared in terms of accuracy. reliability and stability of the updating process. It is shown that the model updating method using frequency response function is superior to the other methods in view of various updating capabilities.

• 정보보호학회논문지
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• 제26권6호
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• pp.1461-1470
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• 2016

부채널 분석에서 신호처리 기법은 차원 압축이나 잡음 제거를 통해 분석의 효율성과 성능을 높일 수 있는 전처리 기법이다. 특이값 분해를 이용한 신호처리 방법은 신호의 분산 정보나 경향성 등을 이용하여 주 신호 정보를 높이고 잡음신호를 낮출 수 있어, 분석 성능 향상에 큰 도움이 된다. 대표적인 기법은 주성분분석과 선형판별분석 그리고 Singular Spectrum Analysis(SSA)가 있다. 주성분분석과 선형판별분석은 주 신호의 정보를 집약하여 차원 압축을 할 수 있으며, SSA는 본 신호를 주 신호와 잡음 신호로 분해하여 잡음 제거가 가능하다. 세 가지 기법 각각을 사용하거나 조합하여 사용할 경우 성능적인 측면을 비교할 필요가 있으며, 그에 대한 방법론이 필요하다. 본 논문에서는 세 기법을 개별적으로 사용할 경우와 조합하여 사용할 경우의 성능을 비교 분석하였으며, 신호 대 잡음비를 이용한 비교분석 방법론을 제시하였다. 제시한 방법론과 다양한 비교분석 실험을 통해 각 기법의 성능과 효율성을 확인하였다. 이로 인해 부채널 분석 분야의 많은 연구자들에게 유용한 정보를 제공할 것이다.

• Journal of applied mathematics & informatics
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• 제28권3_4호
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• pp.697-710
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• 2010

In this paper, we prove existence of infinitely many positive and concave solutions, by means of a simple approach, to $3^{th}$ order three-point singular boundary value problem {$x^{\prime\prime\prime}(t)=\alpha(t)f(t,x(t))$, 0 < t < 1, $x(0)=x'(\eta)=x^{\prime\prime}(1)=0$, (1/2 < $\eta$ < 1). Moreover with respect to multiplicity of solutions, we don't assume any monotonicity on the nonlinearity. We rely on a combination of the analysis of the corresponding vector field on the phase-space along with Knesser's type properties of the solutions funnel and the well-known Krasnosel'ski$\breve{i}$'s fixed point theorem. The later is applied on a new very simple cone K, just on the plane $R^2$. These extensions justify the efficiency of our new approach compared to the commonly used one, where the cone $K\;{\subset}\;C$ ([0, 1], $\mathbb{R}$) and the existence of a positive Green's function is a necessity.

• Kyungpook Mathematical Journal
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• 제53권2호
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• pp.257-271
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• 2013

In this article, we establish the existence of at least three unbounded positive solutions to a boundary-value problem of the nonlinear singular fractional differential equation. Our analysis relies on the well known fixed point theorems in the cones.