• Journal of Korea Water Resources Association
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• v.40 no.4
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• pp.335-343
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• 2007

Drought characteristics need to be preceded before establishing a drought mitigation plan. In this study, using a Standardized Precipitation Index (SPI), a hydrologic drought was defined as an event during which the SPIs are continuously below a certain truncation level. Then, a methodology of drought frequency analysis was performed to quantitatively characterize droughts considering drought duration and severity simultaneously. The theory of runs was used to model drought recurrence and to determine drought properties like duration and severity. Short historical records usually do not allow reliable bivariate analyses. However, more than hundred years of precipitation data (1770 ${\sim}$ 1907) collected in Chosun Kingdom Age using an old Korean rain gage called Chukwooki can provide valuable information about past events. It is shown that a bivariate gamma distribution well represented the joint probabilistic properties of Korean drought duration and severity. The overall results of this study show that the proposed bivariate drought frequency analysis overcomes the drawbacks of the conventional univariate frequency analysis by providing a consistent representation of the drought recurrent property.

• 한국해양학회지
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• v.29 no.3
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• pp.217-227
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• 1994

From northeast to southwest, discontinuous sand ridges distribute on the western continental shelf of Korean Peninsular. The dimension of sand ridges is 3 to 21 m high, 3.1 to 6.8 km wavelength and 9-64 km long with 0.5 steep slope. they are probably originated and reformed by the intensity of tidal current according to the sea level rise. The characteristics of sand ridges revealed in study area are summarized as follows: (1) The sand ridges line up with the long axes of the tidal current ellipses, indicating a tidal control. (2) these are composed of two sedimentary sequences on the 3.5 kHz seismic profiles and core sediments. The upper sequence characterized by prolonged type is covered with thin veneer of massive fine sand(Mz, 2-3$\phi$) with Olive Gray(5Y 5/2). The lower sequence is characterized by internal reflector type with parallel and discontinuous. It consists of sandy mud or muddy sand(Mz, 5-7$\phi$) with laminar structures. the parallel internal reflectors are truncated on the slope of sand ridges. (3) Asymmetrical sand waves are superimposed on the sand ridges, and facing to the crest. However, symmetrical sand waves lie on the crest. Sand ridges having characteristics above is originated by scouring of tidal current, covered with coarase relict sediments, and modified by sadware.

• Development and Reproduction
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• v.22 no.2
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• pp.143-153
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• 2018

The large extracellular domain of glycoprotein hormone receptors is a unique feature within the G protein-coupled receptors (GPCRs) family. After interaction with the hormone, the receptor becomes coupled to Gs, which, in turn stimulates adenylyl cyclase and the production of cAMP. Potential phosphorylation sites exist in the C-terminal region of GPCRs. The experiments described herein represent attempts to determine the functions of the eel follicle-stimulating hormone receptor (eelFSHR). We constructed a mutant of eelFSHR, in which the C-terminal cytoplasmic tail was truncated at residue 614 (eelFSHR-t614). The eelFSHR-t614 lacked all potential phosphorylation sites present in the C-terminal region of eelFSHR. In order to obtain the eelFSHR ligand, we produced recombinant follicle-stimulating hormone ($rec-eelFSH{\beta}/{\alpha}$) in the CHO-suspension cells. The expression level was 2-3 times higher than that of the transient expression of eelFSH in attached CHO-K1 cells. The molecular weight of the $rec-eelFSH{\beta}/{\alpha}$ protein was identified to be approximately 34 kDa. The cells expressing eelFSHR-t614 showed an increase in agonist-induced cAMP responsiveness. The maximal cAMP responses of cells expressing eelFSHR-t614 were lower than those of cells expressing eelFSHR-wild type (eelFSHR-WT). The $EC_{50}$ following C-terminal deletion in CHO-K1 cells was approximately 60.4% of that of eelFSHR-WT. The maximal response in eelFSHR-t614 cells was also drastically lower than that of eelFSHR-WT. We also found similar results in PathHunter Parental cells expressing ${\beta}$-arrestin. Thus, these data provide evidence that the truncation of the C-terminal cytoplasmic tail phosphorylation sites in the eelFSHR greatly decreased cAMP responsiveness and maximal response in both CHO-K1 cells and Path-Hunter Parental cells expressing ${\beta}$-arrestin.

• Journal of Korean Society of Transportation
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• v.25 no.2 s.95
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• pp.17-26
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• 2007

Because the prime objective of the current preemption methods at signalized intersections near highway-railroad grade crossings(IHRGCs) is to clear the crossing, secondary objectives such as safe pedestrian crossing time and minimized delay often are given less consideration or are ignored completely during the preemption. Under certain circumstances state-of-the-practice traffic signal preemption strategies may cause serious pedestrian safety and efficiency problems at IHRGCs. An improved transition preemption strategy(ITPS) that is specifically designed to improve intersection performance while maintaining or improving the current level of safety was developed by Cho and Rilett. Even if the new transition preemption strategy improved both the safety and efficiency of IHRGCs, the performance of the strategy is affected by train speed. Understanding the impact of this factor is essential in order to implement ITPS. In this paper, the effects of train speed were analyzed using a VISSIM simulation model which was calibrated to field conditions. It was concluded that the delay is affected more by train speed than the transitional preemption strategy and the safety of the intersection is not affected by train speed once an advanced preemption warning time(APWT) is equal to or greater than 90 seconds.

• Journal of Korea Water Resources Association
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• v.39 no.4 s.165
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• pp.373-382
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• 2006

In this study a theoretical drought severity-duration-frequency analysis is performed based on a simple Rectangular Pulses Poisson Process Model(RPPM). Data set with various durations are prepared for a given truncation level, whose statistics are then derived to be used for parameter estimation. These parameters are then used for the theoretical drought severity-duration-frequency analysis. The analysis is considered for two cases; one is to consider the overlap probability and the other is not. The drought severity of considering the overlap probability increases more as the return period increases. However, the overlap probability itself decreases as the duration increases, which is because the occurrence probability of events decreases as the duration increases. Also, if the duration increases, the events rarely or even not occur, since parameters of the model cannot be estimated in those cases, so the drought severity may not be computed. This is an obvious limitation of the simple RPPM. In this study the return periods of the important drought events occurred in Seoul are estimated using the results of the study. If the return period of an event is assumed to be the longest one among those with various durations, the return periods of some important event in Seoul are estimated to be between 14 and 35 years. These return periods are not so long to indicate that these droughts can occur frequently.