• The Korean Journal of Applied Statistics
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• v.32 no.4
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• pp.463-483
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• 2019

Since 2000, Korea's total fertility rate (TFR) has been different from that of Japan, Germany, and France where irreversible constants do not change easily in the fertility rate increasing or decreasing phase. It also showed a gradual increase from the minimum fertility level 1.08 in 2005 to 1.23 in 2015, which dropped to 1.17 in 2016, to 1.05 in 2017 and to 0.98 in 2018. This is similar to a double dip in the economic status of a recession. This paper investigates such a TFR increase and decrease factor that predicts the number of births affecting TFR, examines trends in the proportion of married and marital fertility rate broken down by TFR decomposition method. We also examined how these changes affect the change in TFR. According to the results, the number of births is estimated to be between 320 and 330 thousand in 2018, 300 thousand in 2020, 230 and 240 thousand in 2025. The proportion of married is steadily decreasing from 1981 to 2025, and the marital fertility rate is predicted to decline until 2002, then increase from 2003 to 2016 and decrease from 2017 to 2025. Finally, the trend of TFR in terms of number of births, TFR decomposition and statistical model is expected to show 0.98 in 2018, 0.93 to 1.11 in 2020 and 0.76 to 1.08 in 2025.

• Speech Sciences
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• v.8 no.4
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• pp.45-58
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• 2001

Modulated components of a speech signal are frequently used for speech coding, speech recognition, and speech synthesis. Time-frequency representation (TFR) reveals some information about instantaneous frequency, instantaneous bandwidth and boundary of each component of the considering speech signal. In many cases, the extraction of AM-FM components corresponding to instantaneous frequencies is difficult since the Fourier spectra of the components with time-varying instantaneous frequency are overlapped each other in Fourier frequency domain. In this paper, an efficient method decomposing speech signal into AM-FM components is proposed. A variable bandwidth filter is developed for the decomposition of speech signals with time-varying instantaneous frequencies. The variable bandwidth filter can extract AM-FM components of a speech signal whose TFRs are not overlapped in timefrequency domain. Also, amplitude and instantaneous frequency of the decomposed components are estimated by using Hilbert transform.