• Earthquakes and Structures
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• v.18 no.4
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• pp.407-421
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• 2020

In-place analysis for offshore platforms is essentially required to make proper design for new structures and true assessment for existing structures, in addition to the structural integrity of platforms components under the maximum and minimum operating loads when subjected to the environmental conditions. In-place analysis have been executed to check that the structural member with all appurtenance's robustness have the capability to support the applied loads in either storm or operating conditions. A nonlinear finite element analysis is adopted for the platform structure above the seabed and pile-soil interaction to estimate the in-place behavior of a typical fixed offshore platform. The SACS software is utilized to calculate the dynamic characteristics of the platform model and the response of platform joints then the stresses at selected members, as well as their nodal displacements. The directions of environmental loads and water depth variations have significant effects in the results of the in-place analysis behavior. The most of bending moment responses of the piles are in the first fourth of pile penetration depth from pile head level. The axial deformations of piles in all load combinations cases of all piles are inversely proportional with penetration depth. The largest values of axial soil reaction are shown at the pile tips levels (the maximum penetration level). The most of lateral soil reactions resultant are in the first third of pile penetration depth from pile head level and approximately vanished after that penetration. The influence of the soil-structure interaction on the response of the jacket foundation predicts that the flexible foundation model is necessary to estimate the force responses demands of the offshore platform with a piled jacket-support structure well.

• Journal of the Korean Geographical Society
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• v.50 no.2
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• pp.147-164
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• 2015

This study analyzed characteristics and tendencies of seasonal change on shoreline and beach with 8 beaches at East Sea coast by topographical survey for 2 years from March 2012 to February 2013. The shorelines of East Sea coast appeared that amount of seasonal change was bigger than amount of annual change. The seasonal change tendencies between Gangwon-do and Gyeongsangbuk-do coast areas existed some regional differences. To synthesize seasonal changes on 8 beaches of East Sea coast, shoreline advance and beach deposit showed clearly in summer and shoreline retreat and beach erosion showed clearly in autumn. This result is different from tendencies of seasonal change in many mid-latitude coast areas of the world, but generally corresponds with reference studies in west coast and east coast. The major factor of beach erosion showing mostly in summer is storm wave caused by typhoon. The beach erosion by storm wave also occurred in late winter. And it assumes that the beach deposit showing mostly in autumn is result of equilibrium processes of coast area against strong erosion in summer.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.77-85
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• 2009

In South Korea, seasonal, local and temporal climatic characteristics are variable in rainfall patterns. To design or assess the reliability of hydrosystem, information about the rainfall event under consideration is important. In this process, the complete description of a design storm involves the specification of rainfall duration, depth, and its temporal pattern. Generally, to use an appropriate temporal pattern for a design storm is of great importance in the design and evaluation of hydrological safety for hydrosystem. For purpose of selecting of factors affecting the occurrence of rainfall patterns, Huff's dimensionless method was executed and examined by statistical contingency tables analysis through which the inter-dependence of the occurrence frequency of rainfall patterns with respect to geographical location, rainfall duration and depth, and seasonality is investigated. This analysis result can be used to establish flood policies and to design or assess the reliability of hydrosystem.

• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.315-330
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• 2017

Halo coronal mass ejections (CMEs) originating from solar activities give rise to geomagnetic storms when they reach the Earth. Variations in the geomagnetic field during a geomagnetic storm can damage satellites, communication systems, electrical power grids, and power systems, and induce currents. Therefore, automated techniques for detecting and analyzing halo CMEs have been eliciting increasing attention for the monitoring and prediction of the space weather environment. In this study, we developed an algorithm to sense and detect halo CMEs using large angle and spectrometric coronagraph (LASCO) C3 coronagraph images from the solar and heliospheric observatory (SOHO) satellite. In addition, we developed an image processing technique to derive the morphological and dynamical characteristics of halo CMEs, namely, the source location, width, actual CME speed, and arrival time at a 21.5 solar radius. The proposed halo CME automatic analysis model was validated using a model of the past three halo CME events. As a result, a solar event that occurred at 03:38 UT on Mar. 23, 2014 was predicted to arrive at Earth at 23:00 UT on Mar. 25, whereas the actual arrival time was at 04:30 UT on Mar. 26, which is a difference of 5 hr and 30 min. In addition, a solar event that occurred at 12:55 UT on Apr. 18, 2014 was estimated to arrive at Earth at 16:00 UT on Apr. 20, which is 4 hr ahead of the actual arrival time of 20:00 UT on the same day. However, the estimation error was reduced significantly compared to the ENLIL model. As a further study, the model will be applied to many more events for validation and testing, and after such tests are completed, on-line service will be provided at the Korean Space Weather Center to detect halo CMEs and derive the model parameters.

• Journal of the Korean Society for Railway
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• v.8 no.1
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• pp.15-20
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• 2005

The ministry of Environment, Korea, are designing the TMDL(Total Maximum daily Load) program far 4 major large rivers to improve water quality from possible pollutants. It can be successfully performed as controling of nonpoint pollutants from watershed area. Railway stations are stormwater intensive land use because of high imperviousness and high pollutant mass emissions from various activities. Especially the metal pollutants from the railway station were recognized as an important pollutants because of its toxicities. In order to characterize the washed-off pollutants. the monitoring were performed on a railway station during storms. Pollutant concentrations are exponentially decreasing during the storm duration. The 95％ confidence interval of pollutant concentrations in an hour storm duration ranges from 61.6 to 115.4mg/L for TSS(mean=88.50mg/L),103.8-244.1mg/L for COD(mean=174 mg/L) and 7.68-17.32mg/L for Oil & Grease(mean=12.5mg/L). The ranges of metals were 39.2-84.0 $\mu\textrm{g}$/L for total Cu(mean=61.6$\mu\textrm{g}$/L), 14.0-25.8$\mu\textrm{g}$/L for total Pb(mean=19.9$\mu\textrm{g}$/L) and 182.2-376.l $\mu\textrm{g}$/L for total Zn(mean=279.2$\mu\textrm{g}$/L). The first flush criteria for best management practices can be suggested to 50％ pollutant mass emissions during 30％ of the total flow.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.181-181
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• 2018

설계홍수량 산정 시 지점확률강우량을 대상유역 내 면적강우량으로 환산하기 위하여 면적우량 환산계수(areal reduction factor, ARF)를 적용한다. ARF 산정방법은 크게 면적고정형 방법과 호우중심형 방법으로 나뉜다. 면적고정형 방법은 현재 국내 하천설계기준에서 설계강우량 산정 시 활용하고 있는 방법이지만, 동 시간에 발생한 강우사상을 활용하지 않고 지점강우량과 면적강우량의 독립적인 빈도해석을 통해 산정되므로 비현실적인 값이라고 볼 수 있다. 본 연구에서는 강우사상의 공간분포 특성을 효과적으로 반영할 수 있는 레이더 강우 자료를 활용하여 한강권역의 호우중심형 ARF를 활용하였다. 호우중심형 ARF는 지속기간 1, 3, 6, 12, 24시간에 대하여 산정하였으며, 재현기간은 강우 사상의 규모에 따라 총 다섯 구간(0-10, 10-20, 20-50, 50-80, 80-100년)으로 분류하였다. 지속기간 및 재현기간에 따른 호우중심형 ARF는 강우 사상마다 산정되므로 다양한 값이 산재(scattered)되어 있는데, 대푯값을 선정하기 위하여 Weibull 분포의 비초과확률 95%의 값을 추출하였다. 두 가지 방법으로 산정된 ARF는 지속기간에 대하여 로그형태로 증가하였으나, 재현기간에 따른 관계에서는 차이를 보였다. 면적고정형 ARF는 재현기간에 대한 민감도가 매우 낮았으나, 호우중심형 ARF는 재현기간에 따라 감소하였다. 또한 호우중심형 ARF는 지속시간이 길수록 재현기간에 대한 민감도가 점차 낮아졌으며 지속기간 24시간 이후로는 일정한 값을 보였다. 이러한 차이는 레이더 실 강우를 활용한 호우중심형 ARF 산정 시에 면적고정형 ARF 산정과정에서 고려되지 않는 강우의 시 공간적 특성을 반영하기 때문인 것으로 사료된다. 따라서 설계홍수량 산정 시 호우중심형 ARF를 적용한다면 보다 현실적인 값을 제시할 수 있을 것으로 판단된다.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.7-15
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• 2010

Analyses of wind wave characteristics near the Korean marginal seas were performed in 2008 and 2009 by comparisons of an operational wind wave forecast model and ocean buoy data. In order to evaluate the model performance, its results were compared with the observed data from an ocean buoy. The model used in this study was very good at predicting the characteristics of wind waves near the Korean Peninsula, with correlation coefficients between the model and observations of over 0.8. The averaged Root Mean Square Error (RMSE) for 48 hrs of forecasting between the modeled and observed waves and storm surges/tide were 0.540 m and 0.609 m in 2008 and 2009, respectively. In the spatial and seasonal analysis of wind waves, long waves were found in July and September at the southern coast of Korea in 2008, while in 2009 long waves were found in the winter season at the eastern coast of Korea. Simulated significant wave heights showed evident variations caused by Typhoons in the summer season. When Typhoons Kalmaegi and Morakot in 2008 and 2009 approached to Korean Peninsula, the accuracy of the model predictions was good compared to the annual mean value.

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.451-466
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• 2009

While substorms are known to generally occur under southward IMF conditions, they can sometimes occur even under northward IMF conditions. In this paper, we studied the substorms that occurred in May, 2000 to 2002 to examine some statistical characteristics of the IMF and solar wind associated with northward IMF substorms. We focused on the cases where two or more substorms occurred successively under northward IMF conditions. Also, by checking Sym-H index associated with each of the substorms we determined whether or not there is any association of such northward IMF substorm occurrence with storm times. We also examined statistical properties at geosynchronous altitude in terms of magnetic field dipolarization and energetic particle injection. The following results were obtained. (i) Most of the northward IMF substorms occurred under average solar wind conditions. The majority of them occurred within 2 hrs duration of northward IMF Bz state, but there are also a nonnegligible number of substorms that occurred after a longer duraiton of northward IMF Bz state. (ii) While most of the substorms occurred as isolated from a magnetic storm time, those that occurred in a magnetic storm time show a higher average value of IMF and solar wind than that for the isolated substorms. (iii) About 55% of the substorms were associated with the IMF clock angle that can possibly allow dayside reconnection, and the other 45% were associated with more or less pure northward IMF conditions. Therefore, for the latter cases, the energy input from the solar wind into the magnetosphere should be made by other way than the dayside reconnection. (iv) For most of the substorms, the magnetic field dipolarizations and energetic particle injections at geosynchronous altitude were identified to be generally weak. But, several events indicated strong magnetic field dipolarizations and energetic particle injections.

• Journal of Wetlands Research
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• v.11 no.3
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• pp.161-169
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• 2009

Rainfall-runoff procedures of urban area are more complicated than agricultural procedures. Extension and development of town leads to shift of the basin characteristics and it makes more difficult to use runoff models. In this study, the changes of hydrologic circumstances and the shape of hydrograph due to the urbanization in Cho-kyung river basin has been assessed which is the representative urban stream in Jeonju city. The urbanization can be classified as four typical year. The natural basin period(1924) that is before the urban development, the period of construction of Chonbuk National University campus (1963), the period of construction of residential area(1986), and urbanization process has been finally completed in 1995. The rainfall-runoff analysis has been carried out by Storm Water Management Model(SWMM) under condition of the basin characteristics and impervious area of each period. It was found that hydrologic characteristics such as river length, roughness coefficient, and coefficient of surface storage has been decreased. According to the land use change, the pervious area was decreased from 97.7% to 42%, while the impervious area was increased from 0.6% to 34%. The time of concentration was shorten from 90 minutes to 37 minutes. Along with decreasing the time of concentration, the peak discharge was increased from $4.37m^3/s$ to $111.13m^3/s$, and the runoff rate was also increased from 0.8% to 68%.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.945-950
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• 2007

The stormwater runoff from paved area are highly polluted because of particulate materials as well as metals from various vehicular activities. The Division of Road Maintenance in Ministry of Construction and Transportation was recently developed the Guidelines of Environment-kindly Road Maintenance. It is actually requiring the BMP construction to control the nonpoint source pollution as based on the TMDL program. This research is carried out in order to define the characteristics of stormwater runoff from the toll-gate of highways since 2006, which is actually one of the main pollutant sources of paved areas. This monitoring is the first phase work for establishing the treatment facilities in the toll-gates. The one of the main characteristics from toll-gate runoff is the first flush phenomenon containing lots of sediments and metal compounds at the beginning of a storm event. Usually it is used to determine the size of treatment facilities and to calculate the reduced pollutant mass in the facility. The research results shows that the mean EMC vaules for heavy metals are determined to $274.3{\mu}g/L$ for Cd, $1,273.4{\mu}g/L$ for Cr, $1,822.0{\mu}g/L$ for Cu, $6,504.9{\mu}g/L$ for Fe, $14,930.3{\mu}g/L$ for Pb, and $714.1{\mu}g/L$ for Zn. Also the metal mass loadings from the toll-gates are calculated using EMC, watershed area and storm duration.