• The Korean Journal of Applied Statistics
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• v.30 no.6
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• pp.877-888
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• 2017

Spectral analysis is used to determine the frequency of time series data. We first determine the frequency of the series through the power spectrum or the periodogram and then calculate the period of a cycle that may exist in a time series. Estimating the frequency using a Bayesian technique has been developed and proven to be useful; however, the Bayesian estimator for the frequency cannot be analytically solved through mathematical equations and may be handled numerically or computationally. In this paper, we make an inference on the Bayesian frequency through both resampling a parameter by Markov chain Monte Carlo (MCMC) methods and resampling data by bootstrap methods for a time series. We take the Korean real estate price index as an example for Bayesian frequency estimation. We have found a difference in the periods between the sale price index and the long term rental price index, but the difference is not statistically significant.

• Journal of Electrical Engineering and Technology
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• v.6 no.4
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• pp.459-465
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• 2011

A phasor estimation algorithm based on the least square curve fitting technique for the distorted secondary current due to current transformer (CT) saturation is proposed. The mathematical form of the secondary current during CT saturation is represented as the scaled primary current with magnetizing current. The information on the scaled primary current is estimated using the least square technique, with the measured secondary current in the saturated section. The proposed method can estimate the phasor of a fundamental frequency component during the saturated period. The performance of the algorithm is validated under various fault and CT conditions using a C400 CT model. A series of performance evaluations shows that the proposed phasor estimation algorithm can estimate the phasor of the fundamental frequency component with high accuracy, regardless of fault conditions and CT characteristics.

• Economic Analysis
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• v.25 no.4
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• pp.25-57
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• 2019

This paper studies localization effects of knowledge spillovers in Korea using U.S. patents granted over the period 1996-2015. The "sample-matching" analysis initiated by Jaffe, Trajtenberg, and Henderson (1993) is adopted. We do not find evidence of positive localization effects in Korea. In particular, controlling for the existing geographic distribution of knowledge production, the frequency of domestic citations of Korean patents is no more than the citation frequency from overseas, and the difference is decreasing within the sample period. We also examine localization effects across regions and industries, and compare Korea with Taiwan and Japan.

• Journal of Korea Water Resources Association
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• v.48 no.7
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• pp.567-579
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• 2015

This study performed the non-stationary flood frequency analysis considering time-varying parameters of a probability density function. Also, return period and risk under non-stationary condition were estimated. A stationary model and three non-stationary models using Generalized Extreme Value(GEV) were developed. The only location parameter was assumed as time-varying parameter in the first model. In second model, the only scale parameter was assumed as time-varying parameter. Finally, the both parameters were assumed as time varying parameter in the last model. Relative likelihood ratio test and Akaike information criterion were used to select appropriate model. The suggested procedure in this study was applied to eight multipurpose dams in South Korea. Using relative likelihood ratio test and Akaike information criterion it is shown that the inflow into the Hapcheon dam and the Seomjingang dam were suitable for non-stationary GEV model but the other six dams were suitable for stationary GEV model. Also, it is shown that the estimated return period under non-stationary condition was shorter than those estimated under stationary condition.

• Geophysics and Geophysical Exploration
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• v.18 no.1
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• pp.31-34
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• 2015

A gravity meter has been used for exploring subsurface mineral resources and monitoring long-period events such as Earth tides. Recently, researchers found several other intriguing features that we could even detect large teleseismic earthquakes and monitor seismic ambient noise using gravimeters. The zero-length spring suspension technology gives the gPhone (Micro-g LaCoste) excellent low frequency sensitivity, which may have implications for investigating much longer-period natural events (e.g., Earth's hum, tsunami waves, etc.). In this study, we present preliminary results through temporary operation of the gPhone at Geumsan in South Korea for 9 months (Nov. 2008-Jul. 2009). The gPhone successfully recorded large teleseismic events and showed a clear seasonal variation of the Double frequency microseisms during its operation period.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.143-149
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• 2004

We present photometric results for four new variable stars discovered in the vicinity of the ZZ Ceti-type pulsating white dwarf BR Cam. Observations were performed on 5 nights in November 2003 using the 1.8m telescope at Bohyunsan Optical Astronomy Observatory with no filter, on 3 nights in December 2003 using the 0.61m telescope at Sobaeksan Optical Astronomy Observatory with V, I filters, and on 3 nights in October 2004 using the 1.0m telescope at Mt. Lemmon Optical Astronomy Observatory with V, I filters. We estimated their periods from the phase-match technique for one eclipsing binary and the multiple frequency analysis for three pulsating stars. By considering the light curve shape, period and amplitude difference between two passbands, we classified the objects by their variability types as follows: V1 (USNO-A2.0 1425-05691757) is a W UMa-type eclipsing binary with an orbital period of $0^d.4641$; V2 (USNO-A2.0 1425-05703335) is a multi-periodic $\delta$ Set-type pulsating star with a dominant period of $0^d.0649$; V3 (USNO-A2.0 1425-05699659) is also a $\delta$ Set-type pulsating star with a period of $0^d.1408$; and V 4 (USNO-A2.0 1425-05707705) is a RR Lyr-type pulsating star with a period of $0^d.2643$.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.6 s.312
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• pp.105-112
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• 2006

To improve the performance of identification for radars in an ES(Electronic warfare Support) system, it is necessary to estimate scan characteristics as well as the basic identification parameters such as frequency, pulse repetition interval and pulse width of radars. This paper presents the method of estimating the scan period and the scan beam width of circular scanning radars. The proposed method estimates the scan period using the quality of the autocorrelation of a periodic signal. And, it estimates the scan beam width using the linear interpolation and the proposed method of estimating the scan period. Simulation results are presented to show the performance of the proposed method.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.21 no.1
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• pp.95-102
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• 2018

Only the habitat characteristics and breeding status of Paridae have been studied, in addition to the lack of research on Parus varius varius, there is no study on the home-range in the post fledging period. This study was analyzed the home-range size of Parus varius varius in the post fledging period. The survey was conducted in the site located in Dankook Univ. Cheonan Campus(Middle Chungcheong Province). We captured five newborn Parus varius varius using artificial nest was installed before. Radio-tracking was carried out for analysis of home-range, and MCP (Minimum Convex Polygon) was used for analysis. We analyzed 1 individual tracked 15 days (VT5) and 4 individuals which missing radio-tracking transmitter within 3 days (VT1~VT4). Home-range of VT5 gradually increased to 1,38ha, 1.42ha, 2.14ha in the order of early, middle, late period. On the other hand, moving distance was decreased to 174.558m 125.129m, 120.180m. Home-range of V1~VT4 was estimated as 0.81ha which was 75.3% share of home-range of VT5 in early period. As the result it was found that home-range is formed far apart from artificial nest that has been influenced by human being interference, thereafter gradually adapting to interference and spreading close to artificial nest. through this research, we can construct basic ecological data for protecting habitat of Parus varius varius and increasing life rate. As first radio-tracking study of Parus varius varius home-range in the post fledging period, it is expected to be useful for the future study of home-range.

• Journal of Korea Society of Digital Industry and Information Management
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• v.16 no.4
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• pp.75-93
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• 2020

The purpose of this study is to extract keywords for 'startup' and 'entrepreneurship' from Naver news articles in Korea since 1990 and Google news articles in foreign countries, and to understand the changes in the meaning of entrepreneurship and entrepreneurship in each era It is aimed at doing. In summary, first, in terms of the frequency of keywords, venture sprouting is a sample of the entrepreneurial spirit of the government-led and entrepreneurs' chairman, and various technology investments and investments in corporate establishment have been made. It can be seen that training for the development of items and items was carried out, and in the case of the venture re-emergence period, it can be seen that the youth-oriented entrepreneurship and innovation through the development of various educational programs were emphasized. Second, in the result of vocabulary network analysis, the network connection and centrality of keywords in the leap period tended to be stronger than in the germination period, but the re-leap period tended to return to the level of germination. Third, in topic analysis, it can be seen that Naver keyword topics are mostly business-related content related to support, policy, and education, whereas topics through Google News consist of major keywords that are more specifically applicable to practical work.

• Structural Engineering and Mechanics
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• v.40 no.6
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• pp.745-762
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• 2011

Damage detection methodologies based on the direct examination of the nonlinear-nonstationary characteristics of the structure dynamic response may play an important role in online structural health monitoring applications. Different signal processing based damage detection methodologies have been proposed based on the uncovering of spikes in the high frequency component of the structural response obtained via Discrete Wavelet transforms, Hilbert-Huang transforms or high pass filtering. The performance of these approaches in systems subjected to different types of excitation is evaluated in this paper. It is found that in the case of random excitations, like earthquake accelerations, the effectiveness of such methodologies is limited. An alternative damage detection approach using the Continuous Wavelet Transform (CWT) is also evaluated to overcome this limitation. Using the CWT has the advantage that the central frequencies at which it operates can be defined by the user while the frequency bands of the detail functions obtained via DWT are predetermined by the sampling period of the signal.