• The Journal of the Korea Contents Association
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• v.13 no.1
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• pp.48-54
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• 2013

With the development of IT convergence technology and the construction of infrastructure for water leakage detection, the detection technology of damaged pileline's location and size is being spotlighted. The exhaustion of water resource due to the leakage of water supply facilities renders it urgent to detect water leakage effectively. In this paper, we proposed the water leakage detection monitoring simulation using the power spectrum analysis. We measured the reflected wave signal by the proposed water leakage detection monitoring simulation. The rate variability is calculated form the acquired reflected wave signal. And the power spectrum analysis using the Fast Fourier Transform is evaluated the correlation between the water leakage's size and the reflected wave. Ultimately, this paper suggests empirical simulation to verify the adequacy and the validity. Accordingly, the satisfaction and the quality of services will be improved the efficient management by supporting the real-time water leakage detection.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.527-536
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• 2016

This paper investigates seismic damage potential of recent September 12 M5.8 Gyeongju earthquake from diverse earthquake engineering perspectives using the accelerograms recorded at three stations near the epicenter. In time domain, strong motion durations are evaluated based on the accelerograms and compared with statistical averages of the ground motions with similar magnitude, epicentral distance and soil conditions, while Fourier analysis using FFT is performed to identify damaging frequency contents contained in the earthquake. Effective peak ground accelerations are evaluated from the calculated response spectra and compared with apparent peak ground accelerations and the design spectrum in KBC 2016. All these results are used to consistently explain the reason why most of seismic damage in the earthquake was concentrated on low-rise stiff buildings but not quite significant. In order to comparatively appraise the damage potential, the constant ductility spectrum constructed from the Gyeongju earthquake is compared with that of the well-known 1940 El Centro earthquake. Deconvolution analysis by using one accelerogram speculated to be recorded at a stiff soil site is also performed to estimate the soil profile conforming to the response spectrum characteristics. Finally, response history analysis for 39- and 61-story tall buildings is performed as a case study to explain significant building vibration felt on the upper floors of some tall buildings in Busan area during the Gyeongju earthquake. Seismic design and retrofit implications of M5.8 Gyeongju earthquake are summarized for further research efforts and improvements of relevant practice.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.172-177
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• 2013

With Brain Computer Interface (BCI) system, a person with disabled limb could use this direct brain signal like electroencephalography (EEG) to control a device such as the artifact arm. The precise force control for the artifact arm is necessary for this artificial limb system. To understand the relationship between control EEG signal and the gripping force of hands, We proposed a study by measuring EEG changes of three grades (25%, 50%, 75%) of hand grip MVC (Maximal Voluntary Contract). The acquired EEG signal was filtered to obtain power of three wave bands (alpha, beta, gamma) by using fast fourier transformation (FFT) and computed power spectrum. Then the power spectrum of three bands (alpha, beta and gamma) of three classes (MVC 25%, 50%, 75%) was classified by using PCA (Principal Component Analysis) and LDA (Linear Discriminant Analysis). The result showed that the power spectrum of EEG is increased at MVC 75% more than MVC 25%, and the correct classification rate was 52.03% for left hand and 77.7% for right hand.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1818-1825
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• 2017

An Acoustic Doppler Current Profiler(ADCP) measures the current velocity and analyzes the degree of turbulence using Doppler effects of ultrasonic waves. Therefore, the autocorrelation or FFT spectrum estimates are obtained for extraction of current velocity in each spatial region. However, if the correlation method does not satisfy the assumption that the return signal spectra are symmetric Gaussian, the large bias errors can occur. Also, the accurate estimation of autocorrelation or FFT spectrum is difficult due to the short acquisition interval when the rapid changes of current velocity occur. Thus, in this paper, the estimation method of the autoregressive spectrum peak is suggested for the accurate current velocity measurement of both symmetric and asymmetric spectra. It is shown that estimation quality can be improved using the suggested method comparing with the conventional methods. Many return signals under the various environment are simulated and the results are compared and analyzed for evaluation of the suggested method.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.395-403
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• 2022

Flat-panel detector (FPD) used in digital radiographic imaging systems was used to perform a quantitative power spectrum evaluation as a result of the thickness change of polymethyl methacrylate (PMMA), a tissue equivalent. As the PMMA thickness increases with the resolution-chart phantom image, the effect of the scattering line increases, indicating that the modulation characteristics decrease, and the image is bright. The results show that the noise of the image increases, and noise-power spectral images are obtained by Fourier transform to confirm by spatial frequency. Thus, it can be verified that the PMMA thickness and noise are proportional through the result of evaluating the change of resolution characteristics and representing the 2D noise-power spectrum as one-dimensional values by evaluating the change of scattering line with MTF as the PMMA thickness increases in the image.

• Journal of Plant Biotechnology
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• v.33 no.4
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• pp.277-281
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• 2006

Fourier transform - infrared spectroscopy (FT-IR) provides biochemical profiles containing overlapping signals from a majority of the compounds that are present when whole cell extracts are analyzed. We attempted to determine the ripeness of strawberry fruit flesh by FT-IR. Fruit ripeness was divided into four developmental stages based on fruit skin color: 'yellow-green', 'pink-green', 'pink', and 'red' stages. Principal component analysis of FT-IR data of inside fruit flesh extracts clustered samples of four different developmental stages into three discrete groups: (1) 'yellow-green' group, (2) 'pink-green' group, and (3) 'pink' and 'red' group. The most remarkable difference between four different developmental stages was found in the carbohydrate fingerprint region $(1,000-1,100cm^{-1})$ of the FT-IR spectrum, indicating that differences in carbohydrate compounds represented the ripeness of strawberry fruit. Overall results indicate that FT-IR in combination with PCA enables discrimination of the ripeness of strawberry fruit flesh.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.4
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• pp.251-257
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• 2015

In ultrasonic nonlinear parameter measurement using the fast Fourier transform(FFT) of tone-burst signals, the side lobe and leakage on spectrum because of finite time and non-periodicity of signals makes it difficult to measure the harmonic magnitudes accurately. The window function made it possible to resolve this problem. In this study, the effect of the Hanning and Turkey window functions on the experimental measurement of nonlinear parameters was analyzed. In addition, the effect of changes in tone burst signal number with changes in the window function on the experimental measurement was analyzed. The result for both window functions were similar and showed that they enabled reliable nonlinear parameter measurement. However, in order to restore original signal amplitude, the amplitude compensation coefficient should be considered for each window function. On a separate note, the larger number of tone bursts was advantageous for stable nonlinear parameter measurement, but this effect was more advantageous in the case of the Hanning window than the Tukey window.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.241-246
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• 2004

Medical images are being managed more by PACS in general medical institutions. It is important to protect patients from being invaded their privacy related to the images. It is also necessary to confirm the ownership, the right of properity of the medical images and notice whether the data are modified. In this paper, we propose a robust watermarking against RST attacks in medical images on the PACS. The proposed scheme modifies and improves Log-Polar Mapping and Fourier Mellin Transform in order to realize and recover serious image degradation and watermark data loss caused by the conversion between cartesian coordinate and log-polar coordinate. We used the radius and theta Look Up Table to solve the realization of the Fourier Mellin Transform, and inserted a watermark into 2D-DFT magnitudes using Spread Spectrum. Experimental results shows that this method are robust to several attack.

• Journal of Internet of Things and Convergence
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• v.10 no.2
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• pp.17-23
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• 2024

Losses in domestic water supply due to leaks are very large, such as fractures and defects in pipelines. Therefore, preventive measures to prevent water leakage are necessary. We propose the development of a leakage detection sensor utilizing vibration sensors and present an optimal leakage detection algorithm leveraging artificial intelligence. Vibrational sound data acquired from water pipelines undergo a preprocessing stage using FFT (Fast Fourier Transform), followed by leakage classification using an optimized tree-based boosting algorithm. Applying this method to approximately 260,000 experimental data points from various real-world scenarios resulted in a 97% accuracy, a 4% improvement over existing SVM(Support Vector Machine) methods. The processing speed also increased approximately 80 times, confirming its suitability for edge device applications.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.3
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• pp.270-280
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• 2016

This paper investigates the evolution of EM admittance of piezoelectric transducers mounted on a notched beam from wave propagation perspective. A finite element analysis is adopted to obtain numerical solutions for Lamb waves reverberating on the notched beam. The mode-converted Lamb wave signals due to a notch are extracted by using the polarization characteristics of piezoelectric transducers collocated on the beam. Then, a series of temporal spectrums are computed to demonstrate the evolution of EM admittance through fast Fourier transform of the mode-converted Lamb wave signals which are consecutively truncated in the time domain. When truncation time is relatively small, the corresponding temporal spectrum is governed by the characteristics of the input driving frequency. As truncation time becomes large, however, the modal characteristics of the notched beam play a crucial role in the temporal spectrum within the input driving frequency band. This implies that mode-converted Lamb waves reverberating on the beam contributes to the resonance of the beam. The root mean square values are computed for the temporal spectrums in the vicinity of each resonance frequency. The root mean square values increase monotonically with respect to truncation time for any resonance frequencies. Finally the implications of the numerical observation are discussed in the context of damage detection of a beam.