• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5D
• /
• pp.877-884
• /
• 2006

GPS is an essential tool for applications that be required high positioning precision, for the velocity field estimation of tectonic plates. The three years data of eight GPS permanent station were analyzed to estimate crustal deformation velocities using Gipsy-oasis II software. The velocity vectors of GPS stations are estimated by linear regression method in daily solution time series. The velocities have a standard deviation of less than 0.1mm/yr and the magnitude of velocities given by the Korean GPS permanent stations were very small, ranging from 25.1 to 31.1 mm/yr. The comparison between the final solution and other sources, such as IGS velocity result calculated from SOPAC was accomplished and the results generally show good agreement for magnitude and direction in crustal motion. To evaluate the accuracy of our results, the velocities obtained from six plate motion model was compared with the final solution based on GPS observation.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.33 no.3
• /
• pp.122-130
• /
• 2021

A wind-speed estimation at the arbitrary elevations is key component for the design of the offshore wind energy structures and the computation of the wind-wave generation. However, the wind-speed estimation of the target elevation has been carried out by using the typical functions and their typical parameters, e.g., power and logarithmic functions because the available wind speed data is limited to the specific elevation, such as 2~3m, 10 m, and so on. In this study, the parameters of the vertical profile functions are estimated with optimal and analyzed the parameter ranges using the HeMOSU-1 platform wind data monitored at the eight different locations. The results show that the mean value of the exponent of the power function is 0.1, which is significantly lower than the typically recommended value, 0.14. The values of the exponent, the friction velocity, and the roughness parameters are in the ranges 0.0~0.3, 0~10 (m/s), and 0.0~1.0 (m), respectively. The parameter ranges differ from the typical ranges because the atmospheric stability condition is assumed as the neutral condition. To improve the estimation accuracy, the atmospheric condition should be considered, and a more general (non-linear) vertical profile functions should be introduced to fit the diverse profile patterns and parameters.

• Proceedings of KOSOMES biannual meeting
• /
• 2009.06a
• /
• pp.149-150
• /
• 2009

영산강 하구둑에 의해 폐쇄내만의 조건을 가진 영산강 하구역에서 식물플랑크톤의 계절변동을 파악하고자 2008년에 계절별로 7개 정점에서 조사하였다. 영산강 하구역에서 출현한 식물플랑크톤 개체수는 14$\sim$34,958cells/mL의 범위를 보였다. 조사시기별로는 7월에 평균 10,796cells/mL가 출현하여 조사기간 중 가장 많은 출현 개체수를 보였고, 이어서 9월(평균 3,327cells/mL), 5월(평균 590cells/mL), 11월(평균 34cells/mL) 순으로 감소하여 조사시기별 출현개체수의 변동이 매우 심하였다. 규조류는 모든 조사시기에 걸쳐 최고의 점유율을 나타내었고 11월을 제외하면 전체 개체수의 90%이상을 차지하고 있어 규조류가 영산강 하구역의 식물플랑크톤 생물량을 좌우하고 있는 종임을 알 수 있었다. 영산강 하구역에서 출현한 식물플랑크톤의 제 1 우점종은 5월에 Eucampia zodiacus(83.1%), 7월에 Chaetoceros curvisetus(24.2%), 9월에 Pseudo-nitzschia delicatissima(94.3%), 11월에는 Chroomnnas류(33.6%)로 변화하였다. 5월과 9월은 한 종이 전체 식물플랑크톤 개체수의 80% 이상을 차지하는 극우점양상을 보여주었고, 7월에는 C. curvisetus, Skeleton듬 costatum 및 Chaetoceros sp. 등이 유사한 점유율로 우점하고 있었다. 영산강 하구역의 식물플랑크톤 종다양성지수는 0.228$\sim$2.260의 범위로 소수의 우점종에 의해 전체 군집의 분포양상이 결정되는 전형적인 연안, 하구수역의 군집 특성을 보이고 있었다.

• Journal of Korean Ophthalmic Optics Society
• /
• v.11 no.2
• /
• pp.91-97
• /
• 2006

The intraocular pressure for Korean youth were measured by using tonometer (AT555-Reichert). The relative frequency distributions of intraocular pressures have been studied for samples of 1,027 persons(475 males, 552 females). The most commonly recorded IOP for both men and women was around 14.5mmHg and 17.5mmHg, respectively. They were in the range of 7 to 23mmHg(males) and 7 to 22mmHg(females). The median pressure(cumulative frequency=0.5%) is 13.0~16.5mmHg for males and 16.5~18.5mmHg for females, so the values for females are slightly higher than males. The mean pressure is 15.2mmHg for males and 15.8mmHg for females, respectively. The 98% of population was in the range of the normal IOP. There are long-term diurnal variation in mean intraocular pressure and the IOP was decreased as a function of time from morning to night. The measured IOP was affected by several factors: exercise made to decrease the IOP and tight collars, dark places and posture of decubitus position got to elevate the IOP.

• Journal of Korea Water Resources Association
• /
• v.43 no.4
• /
• pp.325-336
• /
• 2010

This study presents the alteration of flow regime by effects of dams and water use in the Geum River Basin. The surface water use rate and the Impounded Runoff (IR) index were examined to assess the pressure indicators of the flow alteration. We applied the flow duration curve, flow regime coefficient, flood and low-flow frequency analysis as well as Range of Variability Approach (RVA) to investigate the quantitative changes in natural flow regimes. The results indicate that the high flow decreased and low flow increased respectively compared to the natural flow regimes at eight gauging stations. The Geum river is regulated by 139 dams and reservoirs storing 24% of the annual mean discharge and has high surface water use rate of 36%. These indicators are main pressure factors to alter flow regimes.

• The Korean Journal of Financial Management
• /
• v.23 no.2
• /
• pp.85-107
• /
• 2006

This paper investigates whether the futures market responds to the news more sensitively and uses more diverse information than the spot market. The sensitivity to the news is measured by the coefficients of the model which regresses the daily changes in the futures prices to the daily changes in the theoretical prices computed from spot prices using the spot-futures parity. The diversity of news is measured by the mean range differences ($\overline{RD}$), mean hi-price differences($\overline{HD}$) and mean low-price differences. The data in this paper is the closing prices of the nearest-to-maturity and the second-nearest-to-maturity contracts of the KOSPI 200 index futures. As the estimates of the relative sensitivity of the futures prices($^{\beta}$) for the whole-period sample are not significantly different from 1, the sensitivity of two markets to the news are not different. However, $\hat{\beta}$ of the most recent period(Nov. 2002 to Dec. 2005) are strongly different from 1. And, in the most recent period, the futures price changes for the good news, which is defined as the price increase of KOSPI of more than 1.5% in a day, show additional sensitivity. Since the mean range different which measures the relative diversity of information used, are not significantly different from 0 for the whole-period and subperiod samples, and this can be interpreted that the futures market does not use more diverse information than the spot market. However, the mean high-price difference, which measures the relative diversity of good news, are significantly different from 0 for the nearest-maturity contracts in the whole-period and subperiod samples. This evidence supports that the futures prices reflects more diverse good news which brings price increase in the market.

• Journal of Korea Water Resources Association
• /
• v.45 no.5
• /
• pp.465-472
• /
• 2012

Recently, as the development of water front and natural type river is gradually increasing, it is mostly the case in that the flow analysis is implemented by only the flood level of the starting point without the tidal effect when the flood water level of the starting point is highly estimated than the high tidal water level in the design of river adjacent to an estuary. This research has analyzed the variation of tidal current for Oncheon river in Busan using Delft-3D program, considering that the tidal effect can cause the change of the flood water level of the starting point although the flood water level is higher than the flood tide level. As a result, considering the tidal effect at downstream boundary condition, water level indicates a periodicity of tide in particular region and the fluctuation range of water level is extended to upstream.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.2
• /
• pp.53-61
• /
• 2009

This paper presents the improved voltage regulation method in power distribution system with multiple PV systems. At present, Line Drop Compensator (LDC) method has been used as voltage regulation method of power distribution system, which regulates the voltage using Under Load Tap Changer (ULTC), regarding the power flow of distribution system as one way. However, the method may be not able to regulate the voltage in a permissible range when the power flow is two ways. Thus, in this paper, we present the improved voltage regulation method of power distribution system using the voltage data of the point connected PV systems.

• The Journal of Engineering Geology
• /
• v.18 no.4
• /
• pp.393-403
• /
• 2008

The relationship between precipitation and groundwater level and the correlation between the moving average of precipitation and goundwater level were analyzed for the southern area of Korean peninsular. There were somewhat different patterns of seasonal fluctuation of groundwater level data. The groundwater level data tends to decrease in dry spell and increase in wet spell however the range between maximum and minimum values is quite different for each gauging point. The maximum correlation coefficient for each gauging station is obtained in a range of 20- to 130-day moving average period of precipitation. The critical infiltration, which is the maximum daily infiltration averaged throughout watershed, value is turned out to have the range of 10 to 90 mm and the moving average period is 10 to 150 days. We could have stronger correlation when we consider critical infiltration and modify the original precipitation data than we use original precipitation data.

• Journal of the Korean earth science society
• /
• v.32 no.7
• /
• pp.719-731
• /
• 2011

Based on the ICE-3G and ICE-5G ice models, we predicted the velocities of crustal uplift caused by Glacial Isostatic Adjustment (GIA) at 39 tide gauge sites operated by Korea Hydrographic and Oceanographic Administration (KHOA). We also divided the Korean peninsula in the ranges of $32-38.5^{\circ}N$ and $124-132^{\circ}E$ in $0.5^{\circ}{\times}0.5^{\circ}$ grids, and computed the GIA velocities at each grid point. We found that the average uplift rates due to GIA in South Korea were 0.33 and 1.21 mm/yr for ICE-3G and ICE-5G, respectively. Because the GIA rates were relatively high at ~1 mm/yr when the updated ice model ICE-5G was used, we concluded that the GIA effect cannot be neglected when we compute the absolute sea level (ASL) rates around the Korean peninsula. In this study, we corrected the ICE-5G GIA velocities from the relative sea level rates provided by KHOA and we computed the ASL rates at 13 tide gauge stations. As a result, we found that the average ASL velocity around the Korean peninsula was 5.04 mm/yr. However, the ASL rates near Jeju island were abnormally higher than the other areas and the average was 8.84 mm/yr.