• Proceedings of the KSME Conference
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• 2004.04a
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• pp.798-803
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• 2004

Leak noise is a good source to identify the exact location of a leak point of underground water pipelines. Water leak generates broadband sound from a leak location and this sound propagation due to leak in water pipelines is not a non-dispersive wave any more because of the surrounding pipes and soil. However, the necessity of long-range detection of this leak location makes to identify low-frequency acoustic waves rather than high frequency ones. Acoustic wave propagation coupled with surrounding boundaries including cast iron pipes is theoretically analyzed and the wave velocity was confirmed with experiment. The leak locations were identified both by the acoustic emission (AE) method and the cross-correlation method. In a short-range distance, both the AE method and cross-correlation method are effective to detect leak position. However, the detection for a long-range distance required a lower frequency range accelerometers only because higher frequency waves were attenuated very quickly with the increase of propagation paths. Two algorithms for the cross-correlation function were suggested, and a long-range detection has been achieved at real underground water pipelines longer than 300m.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.5-11
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• 2006

Cognitive radio, which is designed to dynamically adapt its transmission to its environments is believed to be one of the fundamental techniques for the future spectrum utilization. As the first step of cognitive radio, spectrum sensing is treated as the most important technique. In this paper, we propose a spectral correlation based detection method for spectrum sensing. Based on the cyclostationarity of communication signals, spectral correlation function is used to minimize the effect of random noise and interference. The ROC performance of conventional energy detection is shown. Simulation result show that the proposed detection method outperforms the energy detection and more suitable for spectrum sensing in cognitive radios.

• Journal of Power Electronics
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• v.10 no.6
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• pp.762-768
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• 2010

This paper describes the development of a new islanding detection method for inverter-based distributed generation systems, which uses a signal cross-correlation scheme between the injected reactive current and the power frequency deviation. The proposed method injects 1% of the reactive current to the rated current which brings about a negligible degradation of the power quality. It discriminates the islanding state, when the calculated cross-correlation index is larger than 0.5. The operational feasibility was verified through computer simulations with PSCAD/EMTDC software and experimental research with a hardware prototype. The proposed method can detect the islanding state without degrading the power quality at the point of common connection. Further study is required to overcome the cancellation of the injected reactive current from multiple distributed generation units interconnected with the utility grid.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.327-332
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• 2004

Leak noise is a good source to identify the exact location of a leak point of underground water pipelines. Water leak generates broadband noise from a leak location and can be propagated to both directions of water pipes. This sound propagation due to leak in water pipelines is not a non-dispersive wave any more because of the surrounding pipes and soil. However, the necessity of long-range detection of this leak location makes to identify low-frequency acoustic waves rather than high frequency ones. Acoustic wave propagation coupled with surrounding boundaries including cast iron pipes is theoretically analyzed and the wave velocity was confirmed with experiment. The leak locations were identified both by the acoustic emission (AE) method and the cross-correlation method. In a short-range distance, both the AE method and cross-correlation method are effective to detect leak position. However, the detection for a long-range distance required a lower frequency range accelerometers only because higher frequency waves were attenuated very quickly with the increase of propagation paths. Two algorithms for the cross-correlation function were suggested, and a long-range detection has been achieved at real underground water pipelines longer than loom.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.340_341
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• 2009

This paper suggests a detection scheme of a secondary arc extinction using the peak value of a fault voltage estimated by correlation algorithms. The system implemented in this paper is based on a Korean 765 kV system and the suggested proposed scheme is tested on the system. The performance of the method is analyzed by using Electro-Magnetic Transients Program (EMTP)/ATPDraw.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.8
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• pp.665-670
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• 2016

This paper proposes a repeat-back jamming signal detection scheme using a correlation ratio test metric of a combined pseudo-random noise signal for global navigation satellite systems. The correlation ratio test metric allows for the monitoring of possible distortions in the signal correlation. The proposed scheme is a modified version of the correlation ratio test metric to detect a repeat-back jamming signal in a multipath environment. Through a Monte-Carlo simulation, it is confirmed that the proposed scheme detects almost the whole case, which is received a repeat-back jamming signal under the 6 dB jamming to signal power ratio.

• The Journal of Advanced Prosthodontics
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• v.9 no.6
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• pp.432-438
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• 2017

PURPOSE. The purpose of this study was to evaluate the in vitro validity of quantitative light-induced fluorescence-digital (QLF-D) and laser fluorescence (DIAGNOdent) for assessing proximal caries in extracted premolars, using digital radiography as reference method. MATERIALS AND METHODS. A total of 102 extracted premolars with similar lengths and shapes were used. A single operator conducted all the examinations using three different detection methods (bitewing radiography, QLF-D, and DIAGNOdent). The bitewing x-ray scale, QLF-D fluorescence loss (${\Delta}F$), and DIAGNOdent peak readings were compared and statistically analyzed. RESULTS. Each method showed an excellent reliability. The correlation coefficient between bitewing radiography and QLF-D, DIAGNOdent were -0.644 and 0.448, respectively, while the value between QLF-D and DIAGNOdent was -0.382. The kappa statistics for bitewing radiography and QLF-D had a higher diagnosis consensus than those for bitewing radiography and DIAGNOdent. The QLF-D was moderately to highly accurate (AUC = 0.753 - 0.908), while DIAGNOdent was moderately to less accurate (AUC = 0.622 - 0.784). All detection methods showed statistically significant correlation and high correlation between the bitewing radiography and QLF-D. CONCLUSION. QLF-D was found to be a valid and reliable alternative diagnostic method to digital bitewing radiography for in vitro detection of proximal caries.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.1
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• pp.60-69
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• 2014

Footstep detection using seismic sensors for security is a very meaningful task, but readings can easily fluctuate due to noise in outdoor environment. We propose NSSC method based on nonlinear spectral subtraction and cross-correlation using prime footstep model signal as a footstep signal refining process that enhances the signal-to-noise ratio (SNR) and attenuates noise. After de-noising, a detection event classification method is presented as further refining process to ensure that the detection result is a footstep. To validate the proposed algorithm, representative experiments including sunny and rainy-day cases are demonstrated.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.764-769
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• 1994

This study was performed to obtain fast, consistant and reliable estimation system of bacterial counts of raw milk, which effectively related to the quality of sanitaion and the condition of production at the farm. This study compared regression equation and correlation coefficient relationship between standard plate counts and data of Malthus conductance method for the detection time of total, psychrotrophs, coliform bacterial counts in raw milk. Regression equation (RE) between conductance detection time (Y) and total bacterial log counts (X) was Y=18.27651 - 2.07550X, with correlation coefficient -0.95(n=201). In coliform, RE was Y=9.320848 - 1.15598X with correlation coefficient -0.90 (n=207). Psychrotrophs had the RE of Y=29.96008-3.02487 with correlation coeffecient -0.9 (n=201). This conductance method gave results more quickly and was less labor-intensive than traditional standard plate count method.

• The Journal of the Acoustical Society of Korea
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• v.28 no.4
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• pp.401-407
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• 2009

In this paper, we propose a novel method for the cross-correlation based double-talk detection (DTD), which employing the Gaussian Mixture Model (GMM) in the frequency domain. The proposed algorithm transforms the cross correlation coefficient used in the time domain into 16 channels in the frequency domain using the discrete fourier transform (DFT). The channels are then selected into seven feature vectors for GMM and we identify three different regions such as far-end, double-talk and near-end speech using the likelihood comparison based on those feature vectors. The presented DTD algorithm detects efficiently the double-talk regions without Voice Activity Detector which has been used in conventional cross correlation based double-talk detection. The performance of the proposed algorithm is evaluated under various conditions and yields better results compared with the conventional schemes. especially, show the robustness against detection errors resulting from the background noises or echo path change which one of the key issues in practical DTD.