• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2C
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• pp.210-218
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• 2010

In order to improve the efficiency of frequency bandwidth, various modulation methods such as QAM and PSK have been widely used, and their variation APSK(Amplitude Phase Shift Keying) type modulation methods were proposed and are being used in some satellite communication systems. In this paper, a new constellation method named as $4L^2$-APSK is proposed, which places symbol points circularly as the existing APSK constellations do, but has different number of points and different distance between adjacent points on each layer. An equation for error probability in AWGN channel is also induced for $4L^2$-APSK. In addition, a new Gaussian noise channel is proposed in which noise variances are in the amplitude and in the phase and the two are not equal, and a method of obtaining error probabilities in this channel is also suggested. The equations for error probabilities are verified by computer simulations, and error probabilities of $4L^2$-APSK and QAM are analyzed and compared in the AWGN channel and the proposed noise channel, respectively.

• Journal of radiological science and technology
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• v.44 no.3
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• pp.225-229
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• 2021

The digital image such as medical X-ray and nuclear medicine field mainly contains noise distribution. The noise degree in image degrades image quality. That is why, the noise reduction algorithm is efficient for medical image field. In this study, we confirmed effectiveness of application for median modified Wiener filter (MMWF) algorithm for noise reduction in PET/MR image compared with median filter image, which is used as conventional noise redcution algorithm. The Jaszczak PET phantom was used by using 18F solution and filled with NaCl+NiSO4 fluids. In addition, the radioactivity ratio between background and six spheres in the phantom is maintained to 1:8. In order to mimic noise distribution in the image, we applied Gaussian noise using MATLAB software. To evlauate image quality, the contrast to noise ratio (CNR) and coefficient of variation (COV) were used. According to the results, compared with noise image and images with MMWF algorithm, the image with MMWF algorithm is increased approximately 33.2% for CNR result, decreased approximately 79.3% for COV result. In conclusion, we proved usefulness of MMWF algorithm in the PET/MR images.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.12
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• pp.3242-3265
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• 2023

Ensuring reliability of a machinery system involve the prediction of remaining useful life (RUL). In most RUL prediction approaches, noise is always considered for removal. Nevertheless, noise could be properly utilized to enhance the prediction capabilities. In this paper, we proposed a novel RUL prediction approach based on noise injection and a Kalman filter ensemble of modified bagging predictors. Firstly, we proposed a new method to insert Gaussian noises into both observation and feature spaces of an original training dataset, named GN-DAFC. Secondly, we developed a modified bagging method based on Kalman filter averaging, named KBAG. Then, we developed a new ensemble method which is a Kalman filter ensemble of KBAGs, named DKBAG. Finally, we proposed a novel RUL prediction approach GN-DAFC-DKBAG in which the optimal noise-injected training dataset was determined by a GN-DAFC-based searching strategy and then inputted to a DKBAG model. Our approach is validated on the NASA C-MAPSS dataset of aero-engines. Experimental results show that our approach achieves significantly better performance than a traditional Kalman filter ensemble of single learning models (KESLM) and the original DKBAG approaches. We also found that the optimal noise-injected data could improve the prediction performance of both KESLM and DKBAG. We further compare our approach with two advanced ensemble approaches, and the results indicate that the former also has better performance than the latters. Thus, our approach of combining optimal noise injection and DKBAG provides an effective solution for RUL estimation of machinery systems.

• Journal of The Korean Astronomical Society
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• v.47 no.6
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• pp.255-258
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• 2014

Using sunspot number data from 270 historical stations for the period 1981-2013, we investigate their personal reduction coefficients (k) statistically. Chang & Oh (2012) perform a simulation showing that the k varies with the solar cycle. We try to verify their results using observational data. For this, a weighted mean and weighted standard deviation of monthly sunspot number are used to estimate the error from observed data. We find that the observed error (noise) is much smaller than that used in the simulation. Thus no distinct k-variation with the solar cycle is observed contrary to the simulation. In addition, the probability distribution of k is determined to be non-Gaussian with a fat-tail on the right side. This result implies that the relative sunspot number after 1981 might be overestimated since the mean value of k is less than that of the Gaussian distribution.

• The Journal of the Acoustical Society of Korea
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• v.11 no.2
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• pp.73-84
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• 1992

This paper studies noise subtraction methods and distance measures for speech recognition in a noisy environment, and investigates noise robustness of the distance measures applied to the problem of isolated word recognition in white Gaussian and colored noise (vehicle noise) environments. Noise subtraction methods which can be used as a pre-processor for the speech recognition system, such as the spectral subtraction method, autocorrelation subtraction method, adaptive noise cancellation and acoustic beamforming are studied, and distance measures such and Log Likelihood Ratio ($d_{LLR}$), cepstral distance measure ($d_{CEP}$), weighted cepstral distance measure ($d_{WCEP}$), spectral slope distance measure ($d_{RPS}$) and cepstral projection distance measure ($d_{CP},\;d_{BCP},\;d_{WCP},\;d_{BWCP}$) are also investigated. Testing of the distance measures for speaker-dependent isolated word recognition in a noisy environment indicate that $d_{RPS}\;and\;d_{WCEP}$ which weigh higher order cepstral coefficients more heavily give considerable performance improvement over $d_{CEP}and\;d_{LLR}$. In addition, when no pre-emphasis is performed, the recognizer can maintain higher performance under high noise conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12A
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• pp.949-961
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• 2009

This paper analyses BER (Bit Error Rate) performance of 2-hop wireless communications networks with hybrid decode-and-forward (HDF) relays. The conventional HDF method is usually based on the receive signal-to-noise ratio (SNR) for the relay to decide whether to forward the decoded data in order to obviate the erroneous detection at the relay. In contrast, we propose a new solution of using log-likelihood ratio (LLR) as an efficient alternative to SNR. The approximate BER expressions of different HDF schemes are also derived and verified by Monte-Carlo simulations. In addition, we compute the optimum thresholds for HDF schemes. A variety of numerical results demonstrate that the new LLR-based HDF significantly outperforms the SNR-based HDF for any threshold level and relay location under flat Rayleigh fading channel plus AWGN (Additive White Gaussian Noise).

• The KIPS Transactions:PartB
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• v.8B no.2
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• pp.155-163
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• 2001

In this paper, we propose an image registration method by optimization of mutual information to provide a significant infonnation from multimodality images. The method applies mutual infonnation to measure the statistical dependency'r information redundancy between the image intensities of corresponding pixels in both images, which is assumed to be maximal if the images are geometrically aligned. We show the registration results optimizing mutual information between brain MR image and brain CT image and the comparison results with additive gaussian noise. Since our method uses the native image rather than prior segmentation or feature extraction, no user interaction is required and the accuracy of registration is improved. In addition, it shows the robustness against the noise.

• Structural Engineering and Mechanics
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• v.6 no.1
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• pp.77-93
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• 1998

Some design formulas and design procedures for single and multiple tuned liquid column dampers (TLCDs) are proposed in this study. Previous studies show that if the properties of the TLCD system are properly selected then the TLCD could be as effective as the traditional tuned mass dampers. In addition, the TLCD system offers advantages such as flexibility in terms of installation, little maintenance required, and potentials for multiple usage, etc., which are incomparable by other mechanical types of dampers. In this paper, a set of optimal properties such as length and head loss of a TLCD system are derived under the assumption that the building vibrates in a dominate mode and is subjected to Gaussian white noise excitation. A design procedure for a single TLCD system will be illustrated and discussed. Due to the nonlinearity in the damping term, the TLCD system is sensitive to the loading intensity. This loading sensitivity could limit the application range of the TLCD system. It will be shown in this paper that such a nonlinear effect can be reduced by using multiple TLCDs. As a demonstrative example, the control effects on a flexible building modeled as a single degree-of-freedom system subjected to white noise excitation will be analyzed and discussed using single or multiple TLCDs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.4
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• pp.578-585
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• 2018

In this paper, we propose a classification and theft detection system for human and livestock for various moving objects in a barn. To do this, first, we extract the moving objects using the GMM method. Second, the noise generated when extracting the moving object is removed, and the moving object is recognized through the labeling method. And we propose a method to classify human and livestock using model formation and color for the unique form of the detected moving object. In addition, we propose a method of tracking and overlapping the classified moving objects using Kalman filter. Through this overlap determination method, an event notifying a dangerous situation is generated and a theft determination system is constructed. Finally, we demonstrate the feasibility and applicability of the proposed system through several experiments.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.15-19
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• 2003

In this paper, the bit error rate (BER) performance of the fast frequency hopping/M-ary frequency shift keying system using the clipper receiver is analyzed by using the characteristic function (CF) technique in the presence of n=1 band multitone jamming and additive white Gaussian noise environment. The CFs of the clipper receiver outputs are derived as a infinite series representation using Gamma function and Marcum's Q -function. The analytical results are validated with various simulation results. Performance comparisons with linear combining receiver are shown that the BER performance of the clipper receiver is much better than that of the linear combining receiver In addition, as the clipping level approaches to infinity, it is shown that the clipper receiver simply performs a linear combining without clipping and there exists an optimum value of diversity level (the number of hops per symbol) that maximizes the worst case BER performance of the clipper receiver.