• Journal of the Korea Society of Computer and Information
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• v.18 no.7
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• pp.23-35
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• 2013

This paper proposes an effective technique that is used to automatically extract feature vectors from vibration signals for fault classification systems. Conventional mel-frequency cepstral coefficients (MFCCs) are sensitive to noise of vibration signals, degrading classification accuracy. To solve this problem, this paper proposes spectral envelope cepstral coefficients (SECC) analysis, where a 4-step filter bank based on spectral envelopes of vibration signals is used: (1) a linear predictive coding (LPC) algorithm is used to specify spectral envelopes of all faulty vibration signals, (2) all envelopes are averaged to get general spectral shape, (3) a gradient descent method is used to find extremes of the average envelope and its frequencies, (4) a non-overlapped filter is used to have centers calculated from distances between valley frequencies of the envelope. This 4-step filter bank is then used in cepstral coefficients computation to extract feature vectors. Finally, a multi-layer support vector machine (MLSVM) with various sigma values uses these special parameters to identify faulty types of induction motors. Experimental results indicate that the proposed extraction method outperforms other feature extraction algorithms, yielding more than about 99.65% of classification accuracy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.267-275
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• 2012

In this study, crack growth in a center-cracked plate is predicted under mode I variable amplitude loading, and the result is validated by experiment. Huang's model is employed to describe crack growth with acceleration and retardation due to the variable loading effect. Experiment is conducted with Al6016-T6 plate, in which the load is applied, and crack length is measured periodically. Particle Filter algorithm, which is based on the Bayesian approach, is used to estimate model parameters from the experimental data, and predict the crack growth of the future in the probabilistic way. The prediction is validated by the run-to-failure results, from which it is observed that the method predicts well the unique behavior of crack retardation and the more data are used, the closer prediction we get to the actual run-to-failure data.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.526-528
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• 2005

파장 분할 다중화 방식 (WDM)의 광통신은 중앙 기지국에서 각 가입자에게 서로 다른 파장을 할당하여 동시에 데이터를 전송하는 방식으로서 각 가입자는 할당된 파장을 이용하여 항상 데이터를 송/수신할 수 있고 각 가입자에게 대용량의 데이터를 전송할 수 있을 뿐만 아니라 통신의 보안성이 뛰어나고 성능 향상이 용이하다 따라서 상, 하향(양방향, bidirectional) 3 파장 WDM-필터 소자(Flat band-path filter)는 광 가입자망 구축에서 통신 방송을 융합한 양방향 고화질 멀티미디어 서비스 사업에 반드시 필요로 하는 원천 부품이다. 본 연구에서는 1차원 광자결정을 이용한 저 손실 양방향 3 파장 WDM-필터를 얻을 수 있는 이론적 모델을 설계하고 그에 따라 2-cavity $Ta_2O_5/SiO_2$ 1차원 광자결정체를 제작하고 그 특성을 고찰 하였다. 파장에 따른 투과도 측정 결과 1550nm파장에서 투과되고 1310nm 및 1490nm파장에 대한 차단이 이론값과 일치하였다. 1550nm 파장 대에서 손실이 매우 낮은 flat-투과 밴드가 생성되었다. 특히 입사각도에 따라 flat-band 중심 파장의 변화를 이용하므로 새로운 개념의 WDM 소자로의 응용이 가능하다.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.94-97
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• 2009

본 논문에서는 실제 도로 환경에서의 실시간 차선 인식 방법을 제안한다. 전방주시카메라를 활용하여 촬영한 입력영상으로부터 도로영역에 해당하는 관심영역을 추출하고 반복적인 평균 명도를 측정하여 이진화함으로써 차선 특징을 검출하고 YCbCr 변환한 영상에 대한 실험 임계값을 적용하여 중앙선의 특징을 검출하였다. 이에 Canny 알고리즘을 이용한 에지 추출로 허프 변환시의 작업량을 최소화하였으며 허프 변환하여 얻은 차선 후보군으로부터 각도를 기반으로 필터링하여 통계적으로 우선순위가 높은 선분을 차선으로 인식하였다. 또한 실제 도로 환경에서 수집한 동영상으로 실험한 결과 강건한 차선 인식률을 보였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.7
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• pp.1696-1705
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• 1996

The theory of stack filtering, which is a generalization of median filtering, is used to the detection of intensity edges in noisey images. The proposed approach, called the Difference of Estimates(DoE) approach, is a new formulation of a morphological scheme which has been very sensitive to impulse noise. In this approach, stack filters are applied to a noisy image to obtain local estimates of the dilated and eroded versions of the noise-free image. Thresholding the difference between these two estimates yields the binary edge map. We find that this approach yields results comparable to those obtained with the Canny operator for images with additive Gaussian noise, burt works much better when the noise is impulsive.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.786-791
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• 2012

This paper presents a depth boundary sharpening method for improved view synthesis in 3D video. In depth coding, distortion occurs around object boundaries, degrading the quality of synthesized images. In order to encounter this problem, the proposed method estimates an edge map for each frame to filter only the boundary regions. In particular, a window-based filter is employed to choose the most reliable pixel as the replacement considering three factors: frequency, similarity and closeness. The proposed method was implemented as post-processing of the deblocking filter in JMVC 8.3.Compared to the conventional methods, the proposed method generated 0.49 dB PSNR increase and 16.58% bitrate decrease on average. The improved portions were subjectively confirmed as well.

• Journal of the Korea Society of Computer and Information
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• v.24 no.11
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• pp.29-39
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• 2019

As mobile robot applications increase in real life, the need of low cost autonomous driving are gradually increasing. We propose a novel vision-based real-time lane detection and tracking system that supports autonomous driving of mobile robots in constrained tracks which are designed considering indoor driving conditions of mobile robots. Considering the processing of lanes with various shapes and the pre-adjustment of operation parameters, the system structure with multi-operation modes are designed. In parameter tuning mode, thresholds of the color filter is dynamically adjusted based on the geometric property of the lane thickness. And in the unstable input mode of curved tracks and the stable input mode of straight tracks, lane feature pixels are adaptively extracted based on the geometric and temporal characteristics of the lanes and the lane model is fitted using the least-squared method. The track centerline is calculated using lane models and the motion model is simplified and tracked by a linear Kalman filter. In the driving experiments, it was confirmed that even in low-performance robot configurations, real-time processing produces the accurate autonomous driving in the constrained track.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.2
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• pp.133-141
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• 2024

Considering fluid-structure-soil interactions, a finite-element model for a liquid-storage tank is presented and the nonlinear earthquake response analysis is formulated. The tank structure is modeled considering shell elements with geometric and material nonlinearities. The fluid is represented by acoustic elements and combined with the structure using interface elements. To consider the soil-structure interactions, the near- and far-field regions of soil are modeled with solid elements and perfectly matched discrete layers, respectively. This approach is applied to the seismic fragility analysis of a 200,000 kL liquid-storage tank. The fragility curve is observed to be influenced by the amplification and filtering of rock outcrop motions at the site when the soil-structure interactions are considered.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.5
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• pp.347-352
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• 2013

In impulse noise filtering techniques window size play an important role. Usually, an appropriate window is determined according to the noise density. A small window may not be able to suppress noise properly whereas a large window may remove edges and fine image details. Moreover, the value of the central pixel is estimated by considering all pixels within the window. In this work, contrary to the previous approaches, we propose an iterative impulse noise removal scheme that emphasizes on noise-free pixels within a small neighborhood. The iterative process continues until all noisy pixels are replaced with the estimated pixels. In order to estimate the optimal value for a noisy pixel, a genetic programming (GP) based estimator is evolved that takes few noise-free pixels as input. The estimator is constituent of noise-free pixels, arithmetic operators and random constants. Experimental results show that theproposed scheme is capable of removing impulse noise effectively while preserving the fine image details. Especially, our approach has shown effectiveness against high impulse noise density.

• Geophysics and Geophysical Exploration
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• v.12 no.2
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• pp.192-198
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• 2009

Side scan sonar and SBP (sub-bottom profiler) play a very important role in the survey for seafloor imaging and sub-bottom profiling. In this study, we have acquired side scan sonar and SBP data from the artificial reef area. We applied digital image processing techniques to side scan sonar data in order to improve an image quality. For the enhancement of data quality and image resolution, we applied the typical seismic data processing sequence including gain recovery, muting, spectrum analysis, predictive deconvolution, migration to SBP data. We could easily estimate if artificial reef structures were settled properly and their distribution on the seafloor from the integrated interpretation of side scan sonar and SBP data. From the sampling analysis of seabed sediments, texture filtering of side scan sonar data and SBP data interpretation, we could evaluate the sediment type, distribution and thickness of seafloor sediments in detail.