• The Journal of the Acoustical Society of Korea
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• v.24 no.6
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• pp.325-333
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• 2005

This paper proposes a geoacoustic inversion method for the experimental data or MAPLE 2004 experiment conducted in the East Sea of Korea in 2004 and shows source tracking test results to validate the Proposed inversion method. An objective function is defined as a correlation function of the measured and the simulated transmission loss data. The measured transmission data were obtained using a multi-tonal towed source and VLA. The VFSA (Very Fast Simulated Annealing) is applied to the inversion Problem which optimizes the objective function. After performing the inversion process for the S frequencies tonal data independently. geoacoustic models are constructed. Finally matched-field source tracking is Performed using the inverted parameters to verify them.

• The Journal of the Acoustical Society of Korea
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• v.23 no.4
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• pp.288-295
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• 2004

Detection and localization of a slow and quiet target in shallow water environments is a challenging problem for which it is well known that snapshot is deficient because of a fast and strong interferer. This paper presents waveguide interference filtering technique that mitigate strong interferer problems in adaptive matched field processing. MCM (multiple constraint method) based on NDC (null direction constraint) has been proposed for new spatial interferer filter. MCM-NDC using replica force a interferer component to be filtered through CSDM (cross-spectral density matrix). This filtering have an effect on sidelobe reduction and restoring of signal gain of a quiet target. This technique was applied to a simulation on Pekeris waveguide and vertical array data from MAPLE03 (matched acoustic properties and localization experiment) in the East Sea and was shown to improve SBNR (signal-to-background-and-noise ratio) over the standard MVDR (minimum-variance distortionless response) and NSP (null space projection) technique.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.68-72
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• 2000

Matched field processing technique is performed by considering complex underwater environments. Specially, the performance of minimum variance processor is greatly degraded by eigenvalue problem. In this paper, we propose the minimum variance matched field processor using shaping matrix. This shaping matrix makes that the input covariance matrix is invertible and enhances the desired acoustic source component. It was proved effectively range/depth localization of the proposed method with simulated data and vertical array data collected by NATO SACLANT Center north of the island of Elba off the Italian west coast.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.169-172
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• 1999

Matched field processing technique is performed by considering complex underwater environments. Specially, tile performance of minimum variance processor is greatly degraded by eigenvalue problem. In this paper, we .propose the minimum valiance matched field processor using shaping matrix. This shaping matrix makes that the input covariance matrix is invertible and enhances the desired acoustic source component. It was proved effectively range/depth localization of the proposed method with vertical array data collected by NATO SACLANT Center north of the island of Elba off the Italian west coast.

• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.94-100
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• 2001

When using a sample covariance matrix data in paucity of snapshots, adaptive matched field processing will have problem in inverting covariance matrix due to the rank deficiency. The general solutions are diagonal loading and eigenanalysis methods, but there is a significant bias in the power output. This paper presents a quantitative study of bias of power output and the performance of source localization through the simulation and the measured data analysis in fixed source case using the diagonal loading method for the minimum variance processor. Results show that the bias in power output is reduced and the performance of source localization is improved when the number of snapshots is greater than the number of array sensors.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.339-343
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• 2001

본 연구에서는 수중 음의 전달에 작용하는 기하와 지음향 매개변수들을 전역 최적화(global optimization) 방법인 유전자 알고리듬을 사용하여 추정하려한다. 유전자 알고리듬은 목적함수가 불규칙적인 경우에도 모든 가능한 매개변수들을 조사하지 않으면서 전역 최대치 또는 최소치를 추정할 수 있는 최적화 방법으로, 정합장처리와 관련된 매개변수의 조사에 적합한 방향성 조사법이라 할 수 있다. 유전자 알고리듬을 이용하여 천해 해양환경에서 수치실험을 통해 매개변수 역산의 가능성을 살펴보도록 하였다.

• The KIPS Transactions:PartB
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• v.17B no.4
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• pp.303-308
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• 2010

In this paper, we propose a medical image registration technique combining the gradient vector flow and modified conditional entropy. The registration is conducted by the use of a measure based on the entropy of conditional probabilities. To achieve the registration, we first define a modified conditional entropy (MCE) computed from the joint histograms for the area intensities of two given images. In order to combine the spatial information into a traditional registration measure, we use the gradient vector flow field. Then the MCE is computed from the gradient vector flow intensity (GVFI) combining the gradient information and their intensity values of original images. To evaluate the performance of the proposed registration method, we conduct experiments with our method as well as existing method based on the mutual information (MI) criteria. We evaluate the precision of MI- and MCE-based measurements by comparing the registration obtained from MR images and transformed CT images. The experimental results show that the proposed method is faster and more accurate than other optimization methods.

• The Journal of the Acoustical Society of Korea
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• v.24 no.6
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• pp.301-302
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• 2005

• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.83-88
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• 2001

In this paper, matched field processing algorithm robust to environmental mismatches in an ocean waveguide based on feature extraction is summarized. However, in applying this processor to localize a source there are two preliminary issues to be resolved. One is the number of eigenvectors to be extracted and the other is the number of environmental samples to be used. To determine these issues, the relation between the number of dominant modes propagating in a given ocean waveguide and that of eigenvectors to be extracted is analyzed. Then, the analysis results are confirmed by the subspace analysis. This analysis quantifies the similarity between the subspace spanned by the signal vectors and that spanned by the eigenvectors to be extracted. The error index is defined as a relative difference between the location estimated by the current processor and the real source location. It is identified that in the case of extracting the largest eigenvectors equal to the number of dominant modes in a given environment, the processor localizes the source successfully. From the numerical simulations, it is shown that use of at least 30 environmental samples guarantee stable performance of the proposed processor.

• Annual Conference of KIPS
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• 2003.05a
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• pp.607-610
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• 2003

지문 정합을 할 때 특징점 사이의 거리와 각도가 유사한 순서대로 있는가를 비교하는 알고리즘을 제안한다. 한 점에서 가장 가까운 특징점을 찾고 다시 찾은 점에서 가장 가까운 특징점을 찾는데 이러한 세 개의 특징점들 사이의 거리와 끼인 각도를 기본 요소로 하여 이들의 순차를 특징점 배치도로 정의하여 등록지문에도 유사한 순차가 있는지를 검사한다. 정합 시에 특징점 사이의 거리, 각도 순차가 있는가를 검사하기 때문에 중심점을 찾지 않아도 되며 지문의 이동, 회전에 영향을 받지 않는다.