• Journal of Korea Water Resources Association
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• v.36 no.2
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• pp.153-159
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• 2003

When available rainfall data is not sufficient, a rough tendency of I-D-F relationship appeared frequently. In fact, rainfall intensity on the curve shows abnormally higher value the longer rainfall duration is applied that gives rise to great confusion to apply a rainfall I-D-F relationships curve to a practical work, however, the research work will present a way to solve above mentioned problem by the use of the Box-Cox transformation formula for a given rainfall data. The study came to a conclusion that the Box-Cox transformation formula is satisfied to utilize in a practical work on the ground of analysis for rainfall data of Sancheong and Yeongcheon.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2687-2692
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• 2010

There have been performed many researched for flood magnitude analysis, for example, the Flood-Duration-Frequency relations in the west. Because flood water stage data are more available rather than flood amount data at flood gauge stations of Korea, this study developed Flood water level-Duration-Frequency (Fwl-D-F) curves using rainfall Intensity-Duration-Frequency(I-D-F) curves for the quantitative flood risk assessment in urban watersheds. Fwl-D-F curve is made from water level data for 18 years at Joongrayng bridge station of Joongrayng River basin in Han River drainage area. Fwl-D-F curve can estimate the occurrence frequency for a certain flood elevation, which can be used for urban flood forecasting. It is expected that the flood elevation can be estimated from the forecasted rainfall data using both Fwl-D-F and I-D-F curves.

• Journal of Korea Water Resources Association
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• v.34 no.6
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• pp.577-586
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• 2001

This study proposes a theoretical methodology for deriving a rainfall intensity-duration- frequency (I-D-F) curve using a simple rectangular pulses Poisson process model. As the I-D-F curve derived by considering the model structure is dependent on the rainfall model parameters estimated using the observed first and second order statistics, it becomes less sensitive to the unusual rainfall events than that derided using the annual maxima rainfall series. This study has been applied to the rainfall data at Seoul and Inchon stations to check its applicability by comparing the two I-D-F carves from the model and the data. The results obtained are as followed. (1) As the duration becomes longer, the overlap probability increases significantly. However, its contribution to the rainfall intensity decreases a little. (2) When considering the overlap of each rainfall event, especially for large duration and return period, we could see obvious increases of rainfall intensity. This result is normal as the rainfall intensity is calculated by considering both the overlap probability and return period. Also, the overlap effect for Seoul station is fecund much higher than that for Inchon station, which is mainly due to the different overlap probabilities calculated using different rainfall model parameter sets. (3) As the rectangular pulses Poisson processes model used in this study cannot consider the clustering characteristics of rainfall, the derived I-D-F curves show less rainfall intensities than those from the annual maxima series. However, overall pattern of both I-D-F curves are found very similar, and the difference is believed to be overcome by use of a rainfall model with the clustering consideration.

• Journal of Korea Water Resources Association
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• v.41 no.4
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• pp.379-394
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• 2008

Recently, extreme precipitation events beyond design capacity of hydraulic system have been occurred and this is the causes of failure of hydraulic structure for flood prevention and of severe flood damage. Therefore it is very important to understand temporal and spatial characteristics of extreme precipitation events as well as expected changes in extreme precipitation events and distributional characteristics during design period under future climate change. In this paper, climate change scenarios were used to assess the impacts of future climate change on extreme precipitation. Furthermore, analysis of future extreme precipitation characteristics and I-D-F analysis were carried out. This study used SRES B2 greenhouse gas scenario and YONU CGCM to simulate climatic conditions from 2031 to 2050 and statistical downscaling method was applied to establish weather data from each of observation sites operated by the Korean Meteorological Administration. Then quantile mapping of bias correction methods was carried out by comparing the simulated data with observations for bias correction. In addition Modified Bartlett Lewis Rectangular Pulse(MBLRP) model (Onof and Wheater, 1993; Onof 2000) and adjust method were applied to transform daily precipitation time series data into hourly time series data. Finally, rainfall intensity, duration, and frequency were calculated to draw I-D-F curve. Although there are 66 observation sites in Korea, we consider here the results from only Seoul, Daegu, Jeonju, and Gwangju sites in this paper. From the results we found that the rainfall intensity will be increased and the bigger intensity will be occurred for longer rainfall duration when we compare the climate conditions of 2030s with present conditions.

• Journal of the Korean Mathematical Society
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• v.57 no.1
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• pp.89-111
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• 2020

In the present paper, we give some characterization of the L₂ maximal estimate for the operator P^t_a,γf(Γ(x, t)) along curve with complex time, which is defined by $$P^t_{a,{\gamma}}f({\Gamma}(x,t))={\displaystyle\smashmargin{2}{\int\nolimits_{\mathbb{R}}}}\;e^{i{\Gamma}(x,t){\xi}}e^{it{\mid}{\xi}{\mid}^a}e^{-t^{\gamma}{\mid}{\xi}{\mid}^a}{\hat{f}}({\xi})d{\xi}$$, where t, γ > 0 and a ≥ 2, curve Γ is a function such that Γ : ℝ×[0, 1] → ℝ, and satisfies Hölder's condition of order σ and bilipschitz conditions. The authors extend the results of the Schrödinger type with complex time of Bailey [1] and Cho, Lee and Vargas [3] to Schrödinger operators along the curves.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.341-341
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• 2012

최근 기후변화로 인한 이상호우의 발생으로 도시유역에서의 홍수피해가 급증하고 있으며 이로 인해 도시유역에서의 설계홍수량 산정이 매우 중요시 되고 있다. 지금까지는 도시유역에서의 설계홍수량을 산정하기 위해 I-D-F 곡선을 이용하고 있으나 현실적으로 시간단위 이하의 관측강우량 자료의 부족으로 인해 신뢰성 있는 시간단위 이하의 설계강우량 산정에 많은 불확실성을 지니고 있다. 도시유역의 경우에는 자연유역에 비해 강우발생시 일반적으로 도달시간이 한 시간 이하이기 때문에 극한 강우사상 즉, 단시간에 집중적으로 많은 양의 강우가 발생 할 경우 시간단위 이하의 강우강도를 이용한 유출해석이 필요하다. 따라서 본 연구에서는 추계학적 강우발생기법을 통해 시간단위 강우시계열자료를 확충한 후 분해기법을 통해 시간단위이하강우를 생성하였다. 이를 위해 Bartlett-Lewis rectangular pulse 모형과 Cascade 분해 기법을 이용하여 5분단위 강우량자료를 모의발생 하였다. 또한 모의치와 관측치를 재현기간별로 비교, 분석하여 그 차이를 확인하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.5
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• pp.465-475
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• 2020

I-D-F curves were induced by Box-Cox transformation using rainfall data from five major cities in Korea: Seoul, Busan, Daegu, Daejeon, and Gwangju, as well as from Sancheong (South Gyeongsang province) and Yeongcheon (North Gyeongsang province) stations. The practicality of the Box-Cox transformation is more scalable than the traditional method of frequency analysis in terms of applicability because it is available even if the analysis data are insufficient to perform general frequency analysis and do not produce an appropriate probability density function. For the case in which rainfall data for the entire period (10-1440 minutes) and short-term period (20, 30, 40, 50 minutes) at the foregoing 7 stations are omitted, there was a relative error of -23.0 % to 14.7 % at a duration of 10 to 60 minutes below the 100-year frequency. Accordingly, rainfall analysis requires inducing I-D-F curves, including for the short term (20, 30, 40, 50 minutes), and if rainfall data are omitted for the short term (20, 30, 40, 50 minutes), it is necessary to increase the existing margin rate depending on the point in order to ensure the safe design of small-scale hydraulic structures.

• Journal of the Korean Magnetics Society
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• v.13 no.1
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• pp.36-40
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• 2003

We have grown D $y_{x}$B $i_{3-x}$F $e_{5}$ $O_{12}$ (x = 0.5,1.0, 1.5,2.0) magnetic garnet thin films upon $Al_2$O3i and GGG substrate using Pechini process. The annealing temperature to get single phase D $y_{x}$B $i_{3-x}$F $e_{5}$ $O_{12}$ garnet is dependent on substrate, i.e. the annealing temperature for GGG substrate il 5$0^{\circ}C$ lower than that for $Al_2$ $O_3$ substrate. The grains of garnet thin film grown on GGG (111) plane align along [111] direction, and in this case the hysteresis curve does not saturate up to H : 5000 Oe. We attribute this phenomenon to rotation magnetization process. The maximum amount of Bi substitution in polycrystalline D $y_{x}$B $i_{3-x}$F $e_{5}$ $O_{12}$ thin film prepared by Pechini process is restricted to 2.0 Bi atom/unit cell, and this value is less than that in single garnet crystall grown by LPE method.own by LPE method.ethod.

• Journal of the Korean Society of Clothing and Textiles
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• v.23 no.3
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• pp.353-360
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• 1999

An investigation made of the variations of angle of bias on the top of the sleeve cap curve line and calculated easing contraction ratio by capheights(A ; a,h$\times$5,/6) B: A, H/4 +4cm C:A.H/3 D: A.H/ 4+3cm E:AH/4+2cm, F: A,H/4+1cm, G: A,H/4, H:A,H/6, I:A,H/8) and the efects of easing contraction on the cap curve lines of sleeve A, D, G by easing stitch density with the gathering foot: sewing condition-lockstitch industrial machine stitch density(N1.0 ; 38stitches/3cm N1.5: 26stitches/3cm, N2.0 ; 19stitches/3cm, N2.5 ; 14stitches/ 3cm) The results obtained were as follows; 1) The variations of the angle of bias on the top of the sleeve cap curve line by cap heights can be done according to the angle balance (front; $\alpha$-$\beta$ back ; $\alpha$'- $\beta$') between the angle (front ;$\alpha$, $\beta$, back ; $\alpha$'- $\beta$') of bias of the two base-lines. 2) The higher cap height the more higher the calculated easing contraction ratio. 3) The lower the stitch density the higher easing contraction ratio. 4) The effects of easing contraction was that sleeve G was more than sleeve A, D.

• 한국해양학회지
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• v.5 no.1
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• pp.6-13
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• 1970

Ten days and monthly mean temperatures were analysed daily data observed during July, 1916 to March, 1970 statistically. Periodic characters were calculated by Δn, new method of approximate solution of Schuster Method. According to ten days mean temperatures, annual variation function is F($\theta_d$)=16.29-5.27 cos $\theta_d$+0.75 cos2 $\theta_d$-3.14 sin $\theta_d$+1.16 sin2 $\theta_d$-0.63 sin $\3{theta}_d$, where $\theta_d$=$-\frac{\pi}{18}$(d-3), d is the order of ten days period, 1 to 36. Annual mean water temperature is 16.3$^{\circ}C$, minimum in the last ten days of February 10.9$^{\circ}C$, maximum in the last ten days of August 24.5$^{\circ}C$. Periodic character of secular variation shows 11 year and its curve is F($\theta_y$)=16.29+0.53 cos $\theta_y$ -0.16cos $2{\theta}_y$+0.10 cos$3{\theta}_y$-0.10 sin $\theta_y$, where $\theta_y$=2$-\frac{2\pi}{11}$(y-1920), y is calendar year. And the relation between air temperature x and water temprature y is following. y=9.67 1.035$\^x$