• Communications for Statistical Applications and Methods
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• v.18 no.3
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• pp.277-286
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• 2011

Global companies can sell their products with dierent warranty periods based on location and times. Customers can select the length of warranty on their own if they pay an additional fee. In this paper, we consider the warranty period and the repair time limit as random variables. A two-dimensional warranty policy is considered with repair times and failure times. The repair times are considered within the repair time limit and the failure times are considered within the warranty period. Under the non-renewable warranty policy, we obtain the expected number of warranty services and their variances in the censored area by warranty period and repair time limit to conduct a warranty cost analysis. Numerical examples are discussed to demonstrate the applicability of the methodologies and results using field data based on the proposed approach in the paper.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.5 no.4
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• pp.108-114
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• 1972

The present paper deals with secular analysis of zooplankton biomass by statistical method in the south sea of Korea during the period of nine years from 1963 through 1971. Data were taken from the Annual Report of Oceanographic Observations, Fisheries Research and Development Agency, Korea. The trend value of annual variations in the 108 month period above was calculated by method of 12 month moving average, and a period analysis was made by ore of correlogram method using autocorrelation coefficients. The trend of zooplankton biomass shows periodical fluctuation for the period of 63 months with high interrelationships. The seasonal variation has teen obvious with growth phase twice a year, in April and October.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1208-1216
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• 2014

Mismatch between switching frequency and circuit parameters often occurs in industrial applications, which would lead to instability phenomena. The bifurcation behavior of $V^2$ controlled buck converter is investigated as the pulse width modulation period is varied. Nonlinear behavior is analyzed based on the monodromy matrix of the system. We observed that the stable period-1 orbit was first transformed to the period-2 bifurcation, which subsequently changed to chaos. The mechanism of the series of period-2 bifurcations shows that the characteristic eigenvalue of the monodromy matrix passes through the unit circle along the negative real axis. Resonant parametric perturbation technique has been applied to prevent the onset of instability. Meanwhile, the extended stability region of the converter is obtained. Simulation and experimental prototypes are built, and the corresponding results verify the theoretical analysis.

• Communications of the Korean Mathematical Society
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• v.14 no.2
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• pp.405-423
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• 1999

We consider a statistical multiplexer model with finite buffer capacity and finite number of independent identical 3-state bursty voice sources. The burstiness of the sources is modeled by describing both two different active periods (at the rate of one packet perslot) and the passive periods during which no packets are generated. Assuming a mixture of two geometric distributions for active period and a geometric distribution for passive period and geometric distribution for passive period, we derive the recursive algorithm for the probability mass function of the buffer contents (in packets). We also obtain loss probability and the distribution of packet delay. Numerical results show that the system performance deteriorates considerably as the variance of the active period increases. Also, we see that the loss probability of 2-state Markov models is less than that of 3-state Markov models.

• Journal of The Korean Astronomical Society
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• v.43 no.6
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• pp.201-211
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• 2010

We present an analysis of the measurements of mid-eclipse times of V839 Oph, collected from literature sources. Our analysis indicates a period increase of $3.2{\times}10^{-7}$ day/yr. This period increase of V839 Oph can be interpreted in terms of mass transfer of rate $1.76{\times}10^{-7}M_{\odot}/yr$, from the less to the more massive component. The O - C diagram shows a damping sine wave covering two different complete cycles of 36.73 yr and 19.93 yr with amplitudes approximately equal to 0.0080 and 0.0043 day, respectively. The third cycle has to be expected to cover about 13.5 years with lower amplitude than those of the former two cycles. These unequal duration cycles show a non periodicity which may be explained as resulting from either the presence of a tertiary component to the system or cyclic magnetic activity variations due to star spots. For the later mechanism, the obtained characteristics are consistent when applying Applegate (1992) mechanism.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.10
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• pp.127-133
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• 2019

Damage to high-rise buildings caused by earthquakes is less frequency due to small distribution of high-rise buildings and low transmissibility of seismic motion to high-rise buildings. However, demand for high-rise buildings is increasing for development of construction technology and efficient land use. In addition, if high-rise buildings are constructed on soft ground such as landfill, transmissibility of seismic motion due to long-periodization of seismic waves is likely to increase. Thus, with development of technology, buildings are required to expand range of seismic design such as safety for long-period seismic waves. Therefore, in this study, dynamic experiments were performed to evaluate response characteristics of high-rise buildings according to period characteristics of seismicwaves and time history analysis was performed to verify them.

• Journal of Koreanology Reviews
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• v.3 no.1
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• pp.1-6
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• 2024

The Joseon Dynasty lasted for 618 years, from 1392 to 1910, and is regarded as one of the development periods of Korea in various areas, including politics, culture, economy, and society. During this period, the government undertook various measures to try to change the state of the economy and generally transform people's living standards. These were some of the strategies founded on Confucianism, which focused on the right way to govern and manage the economy to attain prosperity for the society. The present study explores government development strategies for improving the economy in Joseon Dynasty period using comprehensive literature analysis via Kci, Scopus, Web of Science databases. Indeed, agricultural transformations during the Joseon dynasty clearly show that knowledge and innovation were critical for encouraging agricultural growth. Therefore, today's South Korean government can implement technological advancement and research to improve its agricultural value chain and food security. Many farmers lack knowledge about improved methods of practicing agriculture or have inadequate capital to invest in research and development; these issues can be dealt with by the relevant government agencies putting in place necessary policies and creating awareness through educational programs and articles.

• Structural Engineering and Mechanics
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• v.31 no.2
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• pp.211-223
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• 2009

Transient response analysis can be conducted either in the time domain, or via the frequency domain. Sometimes a frequency domain method (FDM) has advantages over a time domain method. A practical issue in the FDM is to find out an appropriate extended period, which may be affected by several factors, such as the excitation duration, the system damping, the artificial damping, the period of interest, etc. In this report, the extended period of the FDM based on the Duhamel's integral is investigated. This Duhamel's integral based FDM does not involve the unit impulse response function (UIRF) beyond the period of interest. Due to this fact, the ever-lasting UIRF can be simply set as zero beyond the period of interest to shorten the extended period. As a result, the preferred extended period is the summation of the period of interest and the excitation duration. This conclusion is validated by numerical examples. If the extended period is too short, then the front portion of the period of interest is more prone to errors than the rear portion, but the free vibration segment is free of the wraparound error.

• Earthquakes and Structures
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• v.20 no.4
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• pp.457-471
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• 2021

This study aims at providing a simple and effective methodology to define a meaningful characteristic period for special class of earthquake records named "pulse-like ground motions". In the proposed method, continuous wavelet transform is employed to extract the large pulse of ground motions. Then, Fourier amplitude spectra obtained from the original ground motion and the residual motion is simply compared. This comparison permits to define a threshold pulse-period (Tp∗) as the threshold period above which the pulse component has negligible contributions to the Fourier amplitude spectrum. The effect of pulse on frequency content of motions was discussed on the light of this definition. The advantage and superior features of the new definition were related to the inelastic displacement ratio (IDR) for single-degree-of-freedom systems with period equal to one half of the threshold period. Analyses performed for the proposed period at three ductility levels u=2,4,6 were compared with the results obtained at half of pulse period derived from wavelet analysis, peak-point method and the peak of product of the velocity and the displacement response spectra (Sv x Sd). According to the results, pulse effects on inelastic displacement ratio seem to be more important when $\frac{T_p^*}{T}=2$ (T is the fundamental vibration period of system). The results showed that utilizing of the proposed definition could facilitate an enhanced understanding of pulse-like records features.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.146-149
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• 2008

Simulation and signal conditioning on the time domain surface elevation records are conducted to verify the proposed Welch's method in non-directional ocean wave spectrum analysis. These spectrum data are further conditioned to provide wave characteristic that better describe the sea states. Comparison of significant wave height and zero crossing period between the proposed method and a reference toolkit are presented.