• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.92-100
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• 1995

In this study, the bearing defects were modeled and the vibration of ball bearing faults was presented for the defective pattern. The vibration signal was measured for the single and multiple defected ball bearing at the various defect positions and rotation speed, and then the signal components using the HFRT(high frequency resonance technique) were analyzed by FFT. The experimental data analysis has shown that the frequencies generated in the single or multiple defected ball bearings appear with the characteristic defect frequency and harmonics of ball pass frequency peak. Signal processing by HFRT makes it possible not only to detect the presence of a defect but also to diagnose the defect part of the bearing.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.883-893
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• 2011

In this paper, we propose a novel focus measure that determines in-focus and out-of-focus region in an image. In addition, we achieved extended depth of field by blending the acquired image and Wiener filtered image using a decision map based on the designed focus measure. Since conventional focus measures are based on the amount of high frequency components in an acquired image, the measures may not be accurate if there exist high frequency components in out-of-focused region. To overcome the problem, we designed the novel focus measure based on effective band pass filtering. In simulations and experiments, the proposed method showed better performance than existing methods.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.5
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• pp.365-370
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• 2003

In this paper, a new watermarking algorithm that based on wavelet packet transform is proposed for remote sensing images, which include many high frequency components. It applies watermark to the overall subband that includes the lowest frequency band. Watermark is embedded on original image after selecting the significant wavelet packet coefficients. For selection of significant coefficients which watermarks is embedded on, zerotree algorithm is applied to wavelet packet coefficients using CPSO (Coefficient Partitioning Scanning Order). From the experimental result, the proposed algorithm shows better invisibility and robustness performance compare with conventional watermarking methods. Especially, it demonstrates better robustness for high image compression in the remote images.

• Journal of Broadcast Engineering
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• v.25 no.1
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• pp.58-66
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• 2020

The blur effect, which is generated by various external factors such as out-of-focus and object movement, degrades high-frequency components in the original sharp image. Based on this observation, we propose a novel method for blur detection using textural features. Specifically, the proposed method simultaneously adopts learning-based and watershed-based textural features, which effectively detect the blur on various situations. Moreover, we employ the region-based refinement to improve the processing time while also increasing detection accuracy. Experimental results demonstrate that the proposed method provides the competitive performance compared to previous approaches in literature.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.744-751
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• 2008

In this paper, we investigate methods to enhance the perceptual quality of MP3-coded audios. Based on the high frequency reconstruction method by Liu, in the proposed method, we determine adaptively the starting point of high frequency reconstruction. We also present an improved linear estimation method. For high frequency component generation, we compare two methods. One is a replication of low-frequency components and the other is an insertion of additive white Gaussian noise signals. Through subjective tests, we shall show that the proposed method can improve the perceptual quality of MP3-coded audio.

• The KIPS Transactions:PartB
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• v.8B no.6
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• pp.693-698
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• 2001

Noisy data are often fitted using a smoothing parameter, controlling the importance of two objectives that are opposite to a certain extent. One of these two is smoothness and the other is closeness to the input data. The optimal value of this parameter minimizes the error of the result. This optimum cannot be found exactly, simply because the exact data are unknown. This paper propose the threshold value for noise reduction based on wavelet-thresholding. In the proposed method PSNR results show that the threshold value performs excellently in comparison with conventional methods without knowing the noise variance and volume of signal.

• Journal of the Korean Society of Radiology
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• v.2 no.2
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• pp.17-21
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• 2008

Image quality is improved if the high frequency domains of boundary surface are made distinct. We suggested a method of correcting indistinct defects in ultrasonic images resulting from dynamic imaging. According to the results of the experiment, boundaries in input ultrasonic images became distinct. However, we need to solve the problem that information on pixels of low signal intensity adjacent to boundaries is lost because high-frequency components in the boundaries are strong.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.06a
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• pp.82-83
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• 2019

본 논문에서는 휘도 및 색차 성분에 따른 SHVC 계층간 참조 픽처 생성 방법의 부호화 성능을 분석한다. SHVC 상위 계층에서는 하위 계층의 픽처를 DCT-IF 기반 업샘플링하여 사용한다. 상위 계층의 부호화 성능을 높이기 위해 딥러닝 기반 필터링을 이용하여 휘도, 색차 성분의 고주파 신호 복원이 부호화 성능에 미치는 영향을 분석한다. 기존 Y 성분에만 VDSR 네트워크를 이용하여 필터링을 적용하였을 때보다 색차 성분까지 필터링을 진행할 경우 최대 2.18%, 평균 1.5% 감소된 결과를 보였다.

• Proceedings of the Korea Multimedia Society Conference
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• 2000.04a
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• pp.161-164
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• 2000

본 논문에서는 웨이블릿에 의한 원 영상의 주파수 성분들을 스케일링에 의한 해상도 변화를 이용하여, 여러개의 서브밴드들로 나누어질 수있다는 성질을 이용하여 각각의 서브밴드들을 이용하여 워터마크를 삽입·검출하는 기법을 제안하고 있다. 보통 디지털 워터마크는 크게 주파수 영역 워터마크와 공간 영역 워터마크의 두 가지 분야로 분류될 수 있다. 주파수 영역 워터마크는 영상 데이터를 주파수 공간으로 변환하고 그 주파수 영역들 중에서 인간의 시각에 덜 민감한 성분에 워터마크를 삽입하게 되고, 이는 인간 시각 시스템을 더 효과적으로 활용한 것으로 인간시각으로 감지할 수 없는 영역인 고주파수 성분에 워터마크를 삽입하게된다.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.2
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• pp.159-163
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• 2008

In this paper, a simplified type of adaptive controller using Nussbaum gain for the control of the spacecrapt with elastic appendages is suggested. This method doesn't need the information of the high frequency components in transfer function. While the pitch angle tracks the desired value by this method, the elastic modes are also stabilized. Only pitch angle and the pitch rate are used for the design of the output feedback controller. Especially all system parameters and the high frequency gain are assumed to be unknown. For design simplicity, a controller is designed by using only the linear part, and it's shown to satisfy the nonlinear system by the simulation with basic explanations. By using the Lyapunov function, the stability of the suggested algorithm is demonstrated, and also the effectiveness of the suggested algorithm is verified by showing the computer simulation results.