• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1871-1873
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• 2002

Partial Discharge is radiated in the form of electromagnetic wave from variable sources. It can be taken by UHF antenna and the signal pulse from that has a nonstationary time-series which can be evaluated with several methods. One of them is STFT(short time fourier transform) processed in frequency region. Statistical results using STFT show the possibility being able to discriminate between several PD sources.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.9 s.102
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• pp.1108-1117
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• 2005

A robust damage detection method using short-time Fourier transform and beating phenomena is presented as an estimating tool of the healthiness of large structures. The present technique makes use of beating phenomena that manifest themselves when two signals of similar frequencies are added or subtracted. Unlike most existing methods based on vibration signals, the present approach does not require an analytic model for target structures. Furthermore, the main advantage of the proposed method compared to the competing diagnostic method using vibration data is its robustness. The proposed method is not affected by the amplitude of exciting signals and the location of exciting points. From a measuring view point. the location of sensing point have no influence on the performance of the present method. With a view to verifying the effectiveness of this method. a series of experiments are made and the results show its possibility as a robust damage diagnostic method.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.42-50
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• 1995

This paper proposes a new method to investigate combustion phenomena using the variation of crankshaft speed, From the idea that the variation of crankshaft speed contains the information of combustion, the energy method is applied as a single degree of freedom. Through the comparison of measured and calculated crankshaft speed, the proposed energy model is proved to be effective. When the crankshaft speed is used in the energy equation, filtering of the speed is required. The frequency components of cylinder pressure are analyzed and the coefficients of Fourier series above the twelfth frequency of engine speed are considered as a noise. As an example of application of this research, some combustion analyses like mean effective pressure, heat release rate, and misfire detection were carried out.

• Journal of applied mathematics & informatics
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• v.37 no.5_6
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• pp.507-519
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• 2019

The ground for this paper is to examine the generalized Stokes' first and second issues for an incompressible couple pressure liquid under isothermal conditions. Exact solutions for each problem are acquired by using the Laplace transform (LT) with respect to the time variable t and the sine Fourier transform (FT) with respect to the y-variable. Further, a comparison is given of the obtained results and the results of Devakar and Lyengar [1] and by using the four inverse Laplace transform algorithms (Stehfest's, Tzou's, Talbot, Fourier series) in the space time domain utilizing a numerical methodology. Moreover, velocity profiles are plotted and considered for various occasions and distinctive estimations of couple stress parameters. At the end, the outcomes are exhibited by graphs and in tabular forms.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.05a
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• pp.377-379
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• 2023

Concept drift detection on data stream is the major issue to maintain the performance of the machine learning model. Since the online stream is to be a function of time, the classical statistic methods are hard to apply. In particular case of seasonal time series, a novel window strategy with Fourier analysis however, gives a chance to adapt the classical methods on the series. We explore the KS-test for an adaptation of the periodic time series and show that this strategy handles a complicate time series as an ordinary tabular dataset. We verify that the detection with the strategy takes the second place in time delay and shows the best performance in false alarm rate and detection accuracy comparing to that of arbitrary window sizes.

• Journal of applied mathematics & informatics
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• v.4 no.2
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• pp.529-534
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• 1997

Even though the Shannon wavelet is a prototype of wavelets are assumed to have. By providing a sufficient condition to compute the size of Gibbs phe-nomenon for the Shannon wavelet series we can see the overshoot is propotional to the jump at discontinuity. By comparing it with that of the Fourier series we also that these two have exactly the same Gibbs constant.

• Journal of applied mathematics & informatics
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• v.8 no.2
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• pp.429-437
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• 2001

In [1, 2], described a Chebyshev series method for the numerical solution of integral equations with three automatic algorithms for computing tow regularization parameters, C/sub f/ and r. Here we describe a Fourier series expansion method for a class singular integral equations with Hilbert kernel and constant coefficients with using a new automatic algorithm.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.4
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• pp.33-37
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• 1991

The problem of radiation from a flanged parallel-plate waveguide is re-examined. The technique of the Fourier transform is used to represent the radiation fields in the spectral domain. The simultaneous equations for the radiation field coefficients are formulated and solved to give an asymptotic seolution. The asymptotic series solution is compared with other results, thus clarifying the discrepancy among different numerical approaches.

• Korean Journal of Mathematics
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• v.27 no.2
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• pp.445-463
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• 2019

Let C[0, T] denote the space of continuous real-valued functions on [0, T]. On the space C[0, T], we introduce a Banach algebra of series of functions which are generalized Fourier-Stieltjes transforms of measures of finite variation on the product of simplex and Euclidean space. We evaluate analytic Feynman integrals of the functions in the Banach algebra which play significant roles in the Feynman integration theory and quantum mechanics.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.49.4-49.4
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• 2021

We Present a B and V band time-series CCD photometry of the Delta scuti stars, BV Cnc, BN Cnc, BU Cnc, BS Cnc, in the open cluster M44. The observation was carried out for 36 nights between February, 2020 and February 2021 with a 0.6m telescope equipped 2K CCD camera at Gyeonggi Science High School for the Gifted(GSHS). To detect pulsational frequencies, we wuse Discret Fourier Transformation(DFT) method. We have detected resonable pulsational frequencis compare to previous study.