• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.635-638
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• 2005

The curve shape of the time fluctuation extracted from the electromagnetic signals is very complex. Thus it is important to decide exactly the signal property such as the inflection point for the observed signal. Usually filters elaborately designed are used to detect the signal characteristics. When the noise is added to the signal, the inflection point can be detected using the observation filter. In this paper we propose the design method for a natural observation filter with optimal filter order to extract a definite inflection point for the case of signals with the mixed noise.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1845-1848
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• 2003

PD(Partial Discharge) signal have the range from several kHz to several GHz. External noises don't give any interference to discerning PD signals with high frequency bandwidth between several hundreds MHz to several GHz but, in the range between several decades kHz to several MHz, are big obstacles to prevent from discriminating PD signals. Therefore, selecting appropriate filter to decrease the influence of noise is important problem. PD signals have the characteristics both short duration and non-continuous pulse train. For separating PD signals from External noises, some different filtering methods different from conventional ones are needed and wavelet filtering method was convinced to be suitable filtering method in various investigations. This paper has simulated PD signal and various noises and investigated the influences for the performance of wavelet filter by varying the components relative to designing of wavelet filter and constructed suitable one. For the purpose of convincing the performance of wavelet filter, real PDs were produced in needle to plane electrode structure. This small PD signal was mixed with external noises and filtered with wavelet filter. We have obtained apparent PD signals and noises are well suppressed by wavelet filter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.3
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• pp.464-469
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• 2002

In this research, nonvisibility and robustness of image watermarking mixed Key and Logo method were evaluated. The role of the Key was performed by a personal ID of a copyrighter and the logo images were used as the watermark. The standard image of Lena was used for experimental image and binary images of `Park'with size 32${\times}$32 and 64${\times}$64 were used for the watermark, respectively In order to evaluate nonvisibility of the proposed watermarking scheme, PSNR(Peak Signal to Noise Ratio) of the watermarked image was obtained and for robustness reconstructive rates of the reconstructed watermark were obtained from the watermarked image with image transformation of JPEG lossy compression. The experimental results show that nonvisibility is excellent as PSNR of the watermarked image is 93.75dB and the reconstructive rates of the case of 322${\times}$32 watermark was better than the case of the 64${\times}$64 watermark; average 5.9%, 13.9%, 6.5%, and 4.2% in the case of scale-down rates, rotational rates, impulse noise power density, and JPEG lossy compression rates, respectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.3
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• pp.221-229
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• 2013

In this paper, the image formation by the motion compensation technique for Synthetic Aperture Radar system(SAR) were realized through the computer simulation. The motion compensation technique performed image data with the range compression, the compensation procedure, the azimuth compensation and the noise elimination procedure. The range compression procedure transform the SAR raw data into the frequency domain and correlate with the range reference function and then inversely transform into the time domain. The compensation procedure contain the aircraft fluctuations compensation and the radar image degrading effect elimination procedure which was caused by image formation algorithm itself. The aircraft fluctuations compensation procedure perform the first stage which correct the phase angle and the second stage which calculate the Doppler frequency and determine the coordinate of the received signal. The radar image degrading effect elimination procedure also perform range migration compensation and the image defocussing effect compensation. The azimuth compression procedure transform the compensation data to the frequency domain and correlate with the azimuth reference function. The azimuth correlated data are inversely transformed to the time domain which is called SAR image data. When the above procedure were completed, the image data contains the received signals mixed with noise. The threshold technique was applied to elimination the noise from the mixed image data.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.333-339
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• 2015

In this paper, the surface settlement resulted from the shallow TBM tunnelling has been numerically simulated. TBM tunnelling is especially used in urban area to avoid serious vibration and noise caused by explosion in NATM. Surface settlement is one of the most important problems encountered in all tunnelling and critical in urban areas. In this study, face vibration of TBM excavation is considered to estimate surface settlement trend according to TBM extrusion. The dynamic excavation forces are calculated by total torque on the TBM cutterhead in mixed-face of soil and weathered rock condition with shallow depth. A 3-dimensional FDM code is employed to simulate TBM tunnelling and mechanical-dynamic coupling analysis is performed. The 3D numerical analysis results showed that dynamic settlement histories and trend of surface settlement successfully. The maximum settlement occurred at the excavation point located at 2.5D behind the face, and the effect of face vibration on the surface settlement was verified in this study.

• Convergence Security Journal
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• v.18 no.4
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• pp.62-71
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• 2018

The rapid growth of virtual reality technology in the era of the 4th Industrial Revolution has accelerated scientification of combat training systems in addition to ICT(information and communications technology) in military field. Recently, research and development of simulators based on virtual reality have been actively conducted in order to solve sensitive issues such as increase of civil complaints due to the noise of a shooting range, prevention of shooting accident, and reduction of training cost. In this paper, we propose two key solutions: spatial synchronization method and modified point mass trajectory model with small angle approximation to overcome technical limitations of a current training simulator. A trainee who wears a haptic vest in a mixed reality environment built in MARS(medium-range assault rifle shooting simulator) is able to conduct not only precision shooting but also two-way engagement with virtual opponents. It is possible for trainee to receive more reliable evaluations in the MARS than an existing rifle simulator based on laser.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.3
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• pp.130-135
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• 2006

There have been experiments dealing with the possibility of the actualization of the ANC system by means of operating the DSP adaptation filter. This filter is composed of various filters(including X-LMS algorithm, Filter-U algorithm, and Full-Feedback-Filter-U algorithm) that use ventilation fans and loudspeakers as a primary source in a circular duct as an experimental device. In this operation, the ANC system using the X - LMS algorithm was found to be more effective in reducing noise than without such system. When applying the input signal of the DSP board Full Feedback-Filtered-U algorithm system while having in mind that the additionally installed second control signal was gone through feedback and mixed into the detection microphone installed near the ventilation fan when using the first ventilation fan, the system was not emitted, but maintained stable during the operation of the control filter. At this point, noise tended to decrease at a maximum of l0dB compared to other algorithms at the frequency band of 170-250Hz.

• Journal of the Korean Data and Information Science Society
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• v.21 no.5
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• pp.841-852
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• 2010

An integrated process control (IPC) procedure is a scheme which simultaneously applies the engineering control procedure (EPC) and statistical control procedure (SPC) techniques to reduce the variation of a process. In the IPC procedure, the observed deviations are monitored during the process where adjustments are repeatedly done by its controller. Because the effects of the noise, the special cause, and the adjustment are mixed, the use and properties of the SPC procedure for the out-of-control process are complicated. This paper considers efficiency of EWMA charts for detecting special causes in an ARMA(1,1) noise model with a minimum mean squared error adjustment policy. And we propose the readjustment procedure after having a true signal. This procedure can be considered when the elimination of the special cause is not practically possible.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.548-554
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• 1985

This research is to find a means of reducing diesel engine combustion noise with none or minimum sacrifice of engine performance by investigating the influence of Cylinder Pressure Level(CPL). For this purpose, modified Wiebe's combustion function, considering the heat release curve as a combustion of both premixed and diffusive combustion portion, was exclusively used to obtain the indicator diagram and computer coeds were developed for the numerical analysis. Following are the results of this research. (1) CPL increases almostly with lag of ignition timing increasing .alpha. and decreasing. theta.$_{d}$, but at the crank angle with the maximal efficiency, CPL is independent of .alpha. and .theta.$_{d}$ with constant value of 200 dB especially at the low frequency. (2) For the constant ignition timing, the effects of .alpha. and .theta.$_{d}$ on CPL were the most significant at the frequency of about 1KHz and 300Hz respectively. (3) For the constant value of .alpha. and .theta.$_{d}$, CPL increases linearly with load but thermal efficiency increase very rapidly with maximum value of load Q$_{T}$=30-40 MJ/Kmol, then starts to decrease slowly. (4) The most effective way of reducing combustion noise without sacrificing thermal efficiency, is to decrease .alpha.. In the case of constant .alpha., there always exists a optimum value of .theta.$_{d}$ with respect to the various compression ratio.o..atio.o..

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2A
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• pp.1-11
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• 2005

S-CDMA is the advanced physical layer modulation techniques of DOCSIS 2.0 specification. S-DMT is another challenging modulation technique for cable modem upstream channel due to the intrinsic robustness for fading and impulse noise. The BER performance of S-DMT and S-CDMA over the mixed channel model of AWGN and impulse noise were evaluated in comparison with TDMA. The mathematical BER derivation and the comparison of those three types of technique were performed based on the ${\varepsilon}-mixture$ non-Gaussian impulse noise model. The results of simulation show good compliance with those of analytic BER derivation. By the results of comparisons, it was verified that the performance of S-CDMA and S-DMT is almost the same, but the performance of S-DMT is far superior to that of TDMA at typical BER range of the practical data communications.