• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.6
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• pp.503-511
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• 2013

This paper presents a speech enhancement method using non-negative matrix factorization. In training phase, we can obtain each basis matrix from speech and specific noise database. After training phase, the noisy signal is separated from the speech and noise estimate using basis matrix in enhancement phase. In order to improve the performance, we model the change of encoding matrix from training phase to enhancement phase using independent Gaussian distribution models, and then use the constraint of the objective function almost same as that of the above Gaussian models. Also, we perform a smoothing operation to the encoding matrix by taking into account previous value. Last, we apply the Log-Spectral Amplitude type algorithm as gain function.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.468-479
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• 2022

To detect targets with active sonar system in the underwater environments, the targets are localized by receiving the echoes of the transmitted sounds reflected from the targets. In this case, reverberation from the scatterers is also generated, which prevents detection of the target echo. To detect the target effectively, reverberation suppression techniques such as pre-whitening based on autoregressive model and principal component inversion have been studied, and recently a Non-negative Matrix Factorization (NMF)-based technique has been also devised. The NMF-based reverberation suppression technique shows improved performance compared to the conventional methods, but the geometry of the transducer and receiver and attenuation by distance have not been considered. In this paper, the performance is improved through preprocessing such as the directionality of the receiver, Doppler related thereto, and attenuation for distance, in the case of using a continuous wave with a bistatic sonar. In order to evaluate the performance of the proposed system, simulation with a reverberation model was performed. The results show that the detection probability performance improved by 10 % to 40 % at a low false alarm probability of 1 % relative to the conventional non-negative matrix factorization.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.4
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• pp.153-159
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• 2011

The MUSIC (MUltiple SIgnal Classification) method estimates the directions of arrival (DOAs) of the signals impinging on a sensor array based on the fact that the noise subspace is orthogonal to the signal subspace. In the conventional MUSIC, an estimate of the basis for the noise subspace is obtained by eigendecomposing the sample matrix, which is computationally expensive. In this paper, we present a simple DOA estimation method which finds an estimate of the signal subspace basis directly from the columns of the sample matrix from which the noise power components are removed. DOA estimates are obtained by searching for minimum points of a cost function which is defined using the estimated signal subspace basis. The minimum points are efficiently found through the Brent method which employs parabolic interpolation. Simulation shows that the simple estimation method virtually has the same performance as the complex conventional method based on the eigendecomposition.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.132-139
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• 1992

This paper presents geometrically nonlinear formulation of shell problems using the three-dimensional curved shell element, which includs large displacements and large rotations. Formulations of the geometrically nonlinear problems can be derived in a variety of ways, but most of them have been obtained by assuming that nodal rotations are small. Hence, the tangent stiffness matrix is derived under the assumptions that rotational increments are infinitesimal and the effect of finite rotational increments have to be considered during the equilibrium iterations. To study the large displacement and large rotation problems, the restrictions are removed and the formulations of the curved shell element including the effect of large rotational increments are developed in this paper. The displacement based finite element method using this improved formulation are applied to the analyses of the geometrically nonlinear behaviors of the single and double curved shells, which are compared with the results by others.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.4
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• pp.275-280
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• 2015

In this paper, we studied for modified MUSIC algorithm of direction of arrival (DOA)estimation. Modified MUSIC algorithm search optimal covariance matrix using singular value decomposition and Bayes method, and desired signals are estimated by updating weight. In order to estimation of desired signals, we used sub spatial method of MUSIC algorithm. General MUSIC algorithm can estimate a desired signal in case of non-correlation signal. But, general MUSIC algorithm in case of correlation signal can not estimate a desired signals and resolution is decreased. Though simulation in case of correlation signal, we analyze to compare proposed MUSIC algorithm with general MUSIC algorithm.

• Journal of Korean Society of Steel Construction
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• v.14 no.3
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• pp.423-432
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• 2002

This study presented analytical and numerical solutions for spatial free vibration of nonsymmetric thin-walled circular curved beams. The closed-form solutions were obtained for in-plane free vibration analylsis of monosymmetric curved beams. Likewise, two types of thin-walled curved beam elements were developed using the third and the fifth order Hermitian polynomials. In order to illustrate the accuracy and usefulness of the present method, this study presented analytical and numerical solution and compared these with the results using the ABAQUS's shell elements. In particular, effects of the thickness-curvature as well as the inextensional condition were investigated on the free vibration of curved beams with nonsymmetric sections.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.351-363
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• 2004

Equation of motion of non conservative system considering mass matrix, elastic stiffness matrix, load correction stiffness matrix by circulatory force's direction change and Winkler and Pasternak foundation stiffness matrix is derived. Also stability analysis due to the divergence and flutter loads is performed. And the influence of internal and external damping coefficient on flutter load is investigated applying the quadratic eigen problem solution. Additionally the influence of non-conservative force's direction parameter, internal and external damping and Winkler and Pasternak foundation on the critical load of Beck's and Leipholz's and Hauger's columns are investigated.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.305-305
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• 2021

XP-SWMM은 EAP-SWMM의 Runoff 기능을 보완하고 2D 해석 기능을 새롭게 추가하여 만든 외산(XP Solutions) 프로그램으로 도시유역 유출량 산정, 우수관거 추적 등과 같은 모의가 가능한 종합 모형이다. 그 중 2차원 분석 기능(2D XP-SWMM)은 연산 결과를 Tu-Flow 모형에 대입한 도시침수 해석모형으로 실무에서 주로 사용되고 있다. 그러나 XP-SWMM은 수량 부분 외에도 수질 부분의 다양한 모형이 통합되어 있어 라이센스 가격이 상당히 높고, 국내 환경에 적합한 모형 수정 등 기술지원을 받기 어렵다는 단점을 갖고 있다. 또한, 실무 활용성이 높은 2차원 분석기능의 경우 모의에 소요되는 시간이 크다는 한계점을 갖고 있다. 2D XP-SWMM 연산의 소요시간이 큰 주요 원인은 계산 시간간격마다 큰 셀수의 행렬 계산을 반복하기 때문이며, 격자를 촘촘하게 설정할수록(행렬의 수가 증가할수록) 수치해석에 소요되는 시간은 기하급수적으로 늘어나게 된다. 2D XP-SWMM 연산은 편미분방정식을 계산하는 모형으로 반복법을 채택하고 있기 때문에 짧은 시간내에 침수해석을 진행해야하는 웹기반 초단기 홍수예경보 시스템 등에 활용하기에는 적합하지 않다. 본 연구에서는 2D XP-SWMM 보다 연산속도를 향상시킨 2차원 도시침수 모형을 개발하였다. 기존 XP-SWMM 중심의 실무 적용성을 유지하고자 XP-SWMM과 동일하게 EPA-SWMM 엔진을 활용하였고 DEM 기반의 지표수 흐름방향 결정 알고리즘을 결합하였다. 본 연구에서 개발한 도시침수 모형 결과를 울산광역시, 청주시 등 도심지에서 발생한 과거 침수피해의 양상과 비교하여 그 타당성을 검증하였다.

• The Journal of the Korea Contents Association
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• v.10 no.8
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• pp.18-25
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• 2010

The study has proposed a method that simultaneously takes advantage of each projection matrix acquired by using column-directional two-dimensional PCA(C2DPCA) and row-directional two-dimensional LDA(R2DLDA). The proposed method can acquire a great secure recognition rate, with no relation to the number of training images, with acquired low-dimensional feature matrixes including both the horizontal and the vertical features of a face. Besides, in the alternate experiment of PCA and LDA to row-direction and column-direction respectively(C2DPCA & R2DLDA, C2DLDA & R2DPCA), we could make sure the system of 2 dimensional LDA with row-directional feature(C2DPCA & R2DLDA) obtain higher recognition rate with low dimension than opposite case. As a result of experimenting that, the proposed method has showed a greater recognition rate of 99.4% than the existing methods such as 2DPCA and 2DLDA, etc. Also, it was proved that its recognition processing is over three times as fast as that of 2DPCA or 2DLDA.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.3
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• pp.617-624
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• 2015

The conflict of opposing pedestrian traffic-flow in a subway station(made up of stair, passageway, and escalator) diminishes the convenience and mobility of its users. In addition, the station's efficiency would be negatively affected by the growth of delay and queue length in pedestrian facilities. As these phenomena have been resulted by the overlapping in pedestrian's traffic-line, the separation of it would alleviate these problems. For the criteria and methodology of separation, this paper has investigated the bi-directional queue length and delay on the entrance of each facility (stair, passageway and escalator). Since the pedestrian flow exists bidirectionally, we have used the weighted average by inflow rate for the delay value. For the optimization of the separation, the Genetic Algorithm has been utilized in order to minimize the delay.