• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.490-500
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• 2000

A new technique for the source location of acoustic emission (AE) in plates whose thichness are close to or thinner than the wavelength has been studied by introducing wavelet transform de-noising technique. The detected AE signals were pre-processed using wavelet transform to be decomposed into the low-frequency, high-amplitude flexural components and the high-frequency, low-amplitude extensional components. If the wavelet transform de-noising was employed, we could successfully filter out the extensional wave component, one of the critical errors of source location in plates by arrival time difference method. The accuracy of source location appeared to be significantly improved and independent of the setting of gain and threshold, plate thickness, sensor-to-sensor distance, and the relative position of source to sensors. Since the method utilizes the flexural component of relatively high amplitude, it could be applied to very large, thin-walled structures in practice.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.7
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• pp.671-676
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• 2016

This study is about design for the Rotational Instrument of the Industry factory which is used management safety and maintenance. We developed the multichannel vibration monitering system of the self-diagnosis for middle level CMS(Condition Monitoring System) market, and that system are new features to the expandability and flexibility. Normally one channel is used for treating one signal, but developed instrument can treat four channel with one signal processing card. One rack have redundant power supply and displace and it can check vibration measurement value in field without computer. Bearing fault detection is fundamental of vibration surveillance, but sometimes can not check with vibration velocity and acceleration. So it need the filtering and the amplitude modulation on the acceleration enveloping technology when irregular vibration is happened. We developed the vibration analysis instrument which is applied such technology. And the development prototype shows activated within the vibration error limit.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.59-263
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• 2003

정보통신의 비약적인 발전에 힘입어 멀티미디어 데이터는 언제 어디서든 전송 받거나 공유할 수 있게 되었다. 아날로그 형태에서 디지털의 아날로그를 형태로 빠르게 대체되고 있으며, 디지털로 신호를 표현하는 방법은 기존 사용하여 표현하는 방법에 비해 많은 장점을 가지고 있다. 하지만 디지털로 된 데이터는 언제 어디서든 대단위 복제가 가능하다. 즉, 저작권 침해, 불법 복제 및 배포, 손쉽게 위조할 수 있다는 점이 그것이다. 디지털 컨텐츠의 불법 복제와 유통은 저작자의 창작 의욕과 수입원을 차단하는 매우 중요한 문제이며, 이를 방지하기 위해서 멀티미디어 데이터의 저작권을 가진 소유자가 원하는 정보를 삽입함으로써 데이터의 저작권 보호와 복사 방지 및 불법적인 유통을 막고자 하는 기술이 개발되고 있다. 디지털 영상 정보의 보호를 위해 디지털 영상의 불법적인 내용 조작을 막고, 영상의 소유권을 보장할 수 있는 방법으로 디지털 워터마크(Digital Watermark)가 있다. 디지털 워터마크는 공개키 알고리즘이나 방화벽 등으로 해독된 영상에 대하여 부가적인 보호를 제공한다. 디지털 영상에 대한 저작권 정보, 배포자 정보 그리고 사용자 정보를 영상에 삽입함으로써 훗날 법적인 문제가 발생하였을 때 해결책을 제시할 수 있다. 본 논문에서는 디지털 영상 데이터의 정보 보호를 위해 주파수 영역에서의 웨이브릿 변환(Wavelet Transform)을 이용한 이미지 적응 디지털 워터마킹(Image-Adaptive Digital Watermarking) 방법을 제안한다. 이미지 적응 웨이브릿(Image-Adaptive Wavelet)은 영상을 주파수적으로 분해하면서 각 대역들의 공간 영역에서의 정보를 함께 지니고 JND(Just noticeable difference)을 포함한다. 이미지 적응 웨이브릿의 이러한 특성을 이용하여 다해상도 분해하고, 손실 압축(toss Compression) 이나 필터링(Filtering), 잡음(Noise) 등에 크게 영향받는 저주파 성분과 인간의 시각적으로 큰 의미를 갖는 고주파 성분의 특성을 이용하여 워터마크를 삽입한다.

• The Korean Journal of Petroleum Geology
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• v.13 no.1
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• pp.17-23
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• 2007

Gravity characteristics are investigated in the vicinity of the DASAN scientific station, located at the Svalbard Archipelago, the Arctic using ArcGP data. Boundary effects of free-air gravity anomalies, which appeared generally at the continental margin, are erased after Bouguer correction was applied. Complete Bouguer anomalies produced after terrain correction by GrOPO30 show that gravity anomalies increase from continent to marine. This phenomena seem to be related to the rise of Moho discontinuity. The cut-off frequency of 0.16 was decided after power spectrum analysis and the gravity anomalies were divided into two parts. Residual anomalies in high frequency part show that characteristics of high values along the faults and of low values related to thick sediments in the continent. Characteristic is low values from basement subsidence of continental slope or thick sediments in the marine. The undulation of Moho discontinuity from 3-D inversion modeling show typical characteristics of continental margin that become higher from Svalbard archipelago to Knipovich ridge bordering Eurasian plate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1224-1228
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• 2003

The use of digital imaging technique and digital contents based on internet has grown rapidly for last several years, and the needs of digital image protection become more important. For the purpose of copyright protection on digital image, the verification of authentication techniques like content authentication, ownership authentication, illegal copy and etc are needs. Digital watermarking, the invisible encryption technique to insert digital watermarking into image, the sophisticated perceptual information should be used for providing transparency and robustness of images on watermarking process. In this paper, we implement the algorithm for preventing forged attack. ownership protection and authentication by transforming the wavelet algorithms in frequency domain in terms of human visual system.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.1
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• pp.49-59
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• 2009

In this paper a watermarking algorithm is proposed to optimize the capacity of the digital watermark insertion in an experimental threshold using the characteristics of human visual system(HVS), adaptive scale factors, and weight functions based on discrete wavelet transform. After the original image is decomposed by a 3-level discrete wavelet transform, the watermarks for capacity optimization are inserted into all subbands except the baseband, by applying the important coefficients from the experimental threshold in the wavelet region. The adaptive scale factors and weight functions based on HVS are considered for the capacity optimization of the digital watermark insertion in order to enhance the robustness and invisibility. The watermarks are consisted of gaussian random sequences and detected by correlation. The experimental results showed that this algorithm can preserve a fine image quality against various attacks such as the JPEG lossy compression, noise addition, cropping, blurring, sharpening, linear and non-linear filtering, etc.

• The Journal of Korean Association of Computer Education
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• v.6 no.4
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• pp.37-47
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• 2003

In this paper. we propose a new digital watermarking technique which uses the self-similarity of OCT(Discrete Cosine Transform) coefficients for the ownership protection of an image, similar coefficients are classified by SOM(Self-Organizing Map) out of Neural Network. The watermark is inserted into the selected cluster among clusters which consist of coefficients. Generally, the inserted watermark in high frequency regions of an image is eliminated by the compression process such as JPEG compressions, and the inserted watermark in low frequency regions of an image causes the distortion of an image quality. Therefore, the watermark is inserted into the cluster that has many coefficients in the middle frequency regions. This algorithm reduces the distortion of an image quality because of inserting the watermark into an image according to the number of coefficients in selected cluster. To extract watermarks from the watermarked image, the selected cluster is used without an original image. In the experiment, the new proposed algorithm have a good quality and endure attacks(JPEG compressions, filtering. zoom in, zoom out, cropping, noises) very well.

• Journal of KIISE:Software and Applications
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• v.33 no.11
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• pp.936-941
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• 2006

To apply object recognition techniques to real environment, illumination compensation method should be developed. As effective illumination compensation model, we focused our attention on Retinex model and illumination-Reflectance model, implemented them, and experimented on their performance. We implemented Retinex model with Single Scale Retinex, Multi-Scale Retinex, and Retinex Neural Network and Multi-Scale Retinex Neural Network, neural network model of Retinex model. Also, we implemented illumination-Reflectance model with reflectance image calculation by calculating an illumination image by low frequency filtering in frequency domain of Discrete Cosine Transform and Wavelet Transform, and Gaussian blurring. We compare their illumination compensation performance to facial images under nine illumination directions. We also compare their performance after post processing using Principal Component Analysis(PCA). As a result, illumination Reflectance model showed better performance and their overall performance was improved when illumination compensated images were post processed by PCA.

• Journal of the Korea Society of Computer and Information
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• v.29 no.2
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• pp.101-108
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• 2024

AI-OCR (Artificial Intelligence Optical Character Recognition) combines OCR technology with Artificial Intelligence to overcome limitations that required human intervention. To enhance the performance of AI-OCR, training on diverse data sets is essential. However, the recognition rate declines when image colors have similar brightness levels. To solve this issue, this study employs Homomorphic filtering as a preprocessing step to clearly differentiate color levels, thereby increasing text recognition rates. While Homomorphic filtering is ideal for text extraction because of its ability to adjust the high and low frequency components of an image separately using a gamma value, it has the downside of requiring manual adjustments to the gamma value. This research proposes a range for gamma threshold values based on tests involving image contrast, brightness, and entropy. Experimental results using the proposed range of gamma values in Homomorphic filtering suggest a high likelihood for effective AI-OCR performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.660-665
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• 2018

Research into underwater wireless networks that enable the monitoring and controlling of the ocean environments has been continuing for disaster prevention and military proposes, as well as for the exploitation of ocean resources throughout the world. A research group led by Hoseo university has been studying a distributed underwater monitoring and controlling network. In this study, we developed an interpolator for acoustic communication between an underwater base station controller and underwater base station, which is included in this network. The underwater acoustic communication provided by this network defines four links whose sampling rates are different. Low power consumption is one of the most important requirements. Therefore, we adopted CIC interpolators, which are known to act as filters with a low power consumption, and some CIC interpolators with an appropriate changing rate were selected depending on the link. However, these interpolators have a large passband drop and wide transition region. To solve these problems, we added a compensator and half-band filter. After verifying the algorithm by using Matlab, we designed and verified it with Verilog-HDL in a ModelSim environment.