• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.3
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• pp.15-21
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• 2003

This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a perforated pipe attached to the open end of a simple shock tube facility. The pressure amplitudes and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are measured and analyzed for the range of the incident weak shock wave Mach number between 1.02 and 1.2. In the experiments. the impulse waves are visualized by a Schlieren optical system for the purpose of understanding their propagation characteristics. The results obtained show that for the near sound field the impulse noise strongly propagates toward the pipe axis, but for the far sound field the impulse noise uniformly propagates toward the omnidirections, indicating that the directivity pattern is almost same regardless of the pipe type. For this non-directivity in the far sound field, it is shown that the perforated pipe has little performance to suppress the impulse noise.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.477-481
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• 2009

In this paper the process of transmitting images signal restore to image corrupted by impulse noise proposed switching mean filter. these filter is differential size using the two state noise detection distinguishes noise pixel and noise free pixel. Follow the detected impulse noise density in the image remove the impulse noise using switching mean filter these substituted pixel in order to non-recursive and recursive form from control process of the next pixel comes to be used with neighbor pixel process. Through the simulation, we compared with the existing methods and capabilties.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.67-71
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• 2003

The propagation characteristics of the impulse wave discharged from the exit of a perforated pipe is investigated through a simple shock tube facility. The pressure histories and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are analyzed for the range of the incident weak shock wave Mach number between 1.02 and 1.2. In the shock tube experiments, the impulse wave are visualized by a Schlieren optical system for the purpose of understanding its propagation characteristics. The experimental results show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the omnidirections, indicating that the directivity pattern is almost same regardless of the pipe type. Especially, it is shown that the perforated pipe has a little performance to reduce the impulse noise only for the near sound field

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.258-261
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• 2006

This study introduces the control of duration time of impulse noises emitted from a high voltage COS fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the peak sound pressure level over 150 dB(A) is generated at the distance of 2m from a COS Fuse. For the purpose of the reduction of impulse noise, in this study, the reactive type silencer has been utilized. And also electrical interrupting test was experimented. From the experimental results, the reactive type silencer has been shown to have the noise reduction of about 13 dB(A). It has been found that the electrical interception performance of the COS fuse was related to the control of the duration time of impulse noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.951-954
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• 2006

This Study introduces the design of a reactive type silencer for reducing impulse noises emitted from a high voltage COS fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the peak sound pressure level above 150dB(A) is generated at the distance of 2m from a COS Fuse. For the purpose of the reduction of impulse noise, in this study. the reactive type silencers have been utilized. The performance of noise reduction for them can be expressed by insertion loss. The reactive silencers have been tested for 23 different types with each different porosity, hole diameter and depth. From the experimental results, it is found that the reactive silencer has an excellent performance to greatly suppress the impulse noise. The one-stage, two-stage and three-stage reactive type silencers have been shown to have the insertion losses of about from 35dB (A) to 25dB(A).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1251-1256
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• 2010

In the transmitting process of image signal processing system, there are several different causes of degradation that have been occuring. The main cause of degradation is attributed to the noise. The most representive method of removing noise of image, which is caused by impulse noise environment, is using the SM filter. At edge, the filter has a special feature which has a tendency to decrease. As a result, we proposed a nonlinear filter using the form of mask and the probability of the impulse noise to restore the image considering edge quality in the impulse noise environment. And through the simulation, we compared with the existings and capabilities.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.477-480
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• 2009

In the process of transmitting images, there are several different underlying causes of degradation that have been occuring. The main underlying cause of the degradation has been attributed to the noise. The most representive method of removal noise of image, which is caused by impulse noise, is using the SM filter. At edge the filter has a special feature which has a tendency to decrease. As a result, this paper we proposed the nonlinear filter using the form of mask and the probability of the impulse noise to restore the image considering edge quality in the impulse noise environment. And through the simulation, we compared with the existing methods and capabilties.

• Journal of KSNVE
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• v.10 no.4
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• pp.642-647
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• 2000

Conventional cepstrum has been widely used to detect echo and fault signals embedded in noise. One of the problems of finding impulse signals using the conventional cepstrum in that it is normally very sensitive to signal to noise ratio (SNR). This paper proposes a signal processing method to detect impulse signal in noisy environment. Because the proposed method minimizes the variance of signal power at a cepstrum domain, it is suggested to be called as minimum variance cepstrum (MV cepstrum). Computer simulations have been performed to understand the characteristics of the MV cepstrum. Both mathematical approach and computer simulations confirmed that the MV cepstrum is a useful technique to detect impulse in noisy environment.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.9
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• pp.429-434
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• 2006

In this paper, detection based - adaptive windowed nonlinear filter(DB-AWNF) is proposed for removing salt-pepper noise in infrared image. This filter is composed of impulse detector and window-size-variable median filters. Impulse detector checks whether current pixel is impulse or not using range function and nonlinear location estimator. If impulse is detected, current pixel is filtered according to four kinds of local masks by use of median filter. If not, current pixel is delivered to output like identity filter. In Qualitative view, the proposed could have removed heavy corrupted noise up to 30% and reserved the details of image. In quantitative view, PSNR was measured. The proposed could have about 12-31[dB] more improved performance than those of median $(3{\times}3)$ filter and 13-29[dB] more improved performance than those of median $(5{\times}5)$ filter.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.959-962
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• 2012

In the process of image acquisition, transmission and storage, image degradation occurs due to various reason, the mainly reason is noise. To restore basic methods used images of impulse noise pollution by SM, AF, CWMF. In this paper, using the modified filter to remove impulse noise. The method consists of detection and noise filtering of the noise signal. For a non-noise signal is intact, the noise signal is filtered according to the algorithm. And then through the simulation is compared with known basic methods, with PSNR as judged by reference.