• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.157-161
• /
• 2011

낙동강하구둑 접근수로에는 상류로부터 유입되는 유사가 유속감소로 인해 하구둑 근처에서 퇴적되는 문제가 발생하고 있다. 퇴적되는 유사를 저감시키기 위한 방법으로 하구둑 건설이후 매년 일정한 통수능 확보를 위해 준설이 수행되어 왔다. 그러나 준설 방법은 많은 비용과 시간이 소모된다는 점에서 효율적이지 못하며, 이를 대체 할 수 있는 적절한 퇴사저감방안 연구가 지금까지 선행연구들을 통해 제안되고 있는 실정이다. 특히 하폭이 급격히 확대되어 유속 감소를 유발하고 유사 퇴적을 야기 시키는 하구둑 상류 2km에서 3km 지점의 하폭을 국부적으로 축소함으로써 효과적으로 퇴사를 저감시킬 수 있을 것으로 나타났다. 그러나 하폭축소로 인하여 홍수발생시 상류의 홍수위가 기존 조건에서 보다 상승할 수 있는 위험성이 있다. 따라서 본 연구에서는 하폭축소 방법으로 인해 발생할 수 있는 상류의 홍수위 상승 위험성을 1차원 수치모형인 HEC-RAS 모형을 이용하여 하폭축소 전 후의 수면곡선을 분석하고자 한다. 연구대상 영역은 낙동강하구둑 상류 12km 구포대교 지점까지이며 하폭축소 구간은 낙동강하구둑 상류 2km에서 3km로 하도 우안 구간의 하폭을 10% 축소하였다. 입력 자료는 낙동강유역 종합치수계획에 명시된 빈도별 유량 및 낙동강하구둑 수위 조건을 적용하였다. 모의결과 30년, 50년, 80년, 200년 빈도별 유량과 수위를 적용한 경우 최대 수위상승이 0.02m이하인 것으로 나타났으며, 500년 빈도의 경우 0.03m의 최대 수위상승 값을 확인할 수 있었다.

• Atmosphere
• /
• v.18 no.4
• /
• pp.287-297
• /
• 2008

The vertical profiles and optical properties of Asian dust are investigated using ground-based measurements from 1998 to 2002. Vertical profiles of aerosol extinction coefficient are evaluated using MPL (Micro Pulse Lidar) data. Optical parameters such as aerosol optical thickness ($\tau$), ${\AA}ngstr\ddot{o}m$ exponent ($\alpha$), single scattering albedo ($\omega$), refractive index, and volume size distribution are analyzed with sun/sky radiometer data for the same period. We can separate aerosol vertical profiles into three categories. First category named as 'Asian dust case', which aerosol extinction coefficient is larger than $0.15km^{-1}$ and dust layer exists from surface up to 3-4km. Second category named as 'Elevated aerosol case', which aerosol layer exists between 2 and 6km with 1-2.5km thickness, and extinction coefficient is smaller than $0.15km^{-1}$. Third category named as 'Clear sky case', which aerosol extinction coefficient appears smaller than $0.15km^{-1}$. and shows that diurnal variation of background aerosol in urban area. While optical parameters for first category indicate that $\tau$ and $\alpha$ are $0.63{\pm}0.14$, $0.48{\pm}0.19$, respectively. Also, aerosol volume concentration is increased for range of 1 and $4{\mu}m$, in coarse mode. Optical parameters for second category can be separated into two different types. Optical properties of first type are very close to Asian dust cases. Also, dust reports of source region and backward trajectory analyses assure that these type is much related with Asian dust event. However, optical properties of the other type are similar to those of urban aerosol. For clear sky case, $\tau$ is relatively smaller and $\alpha$ is larger compare with other cases. Each case shows distinct characteristics in aerosol optical parameters.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.31 no.6_1
• /
• pp.455-461
• /
• 2013

Kompsat-3 is an optical high-resolution earth observation satellite launched in May 2012. The AEISS sensor of the Korean satellite provides 0.7m panchromatic and 2.8m multi-spectral images with 16.8km swath width from the sun-synchronous near-circular orbit of 685km altitude. Kompsat-3 is more advanced than Kompsat-2 and the improvements include better agility such as in-track stereo acquisition capability. This study investigated the characteristic of the epipolar curves of in-track Kompsat-3 stereo images. To this end we used the RPCs(Rational Polynomial Coefficients) to derive the epipolar curves over the entire image area and found out that the third order polynomial equation is required to model the curves. In addition, we could observe two different groups of curve patterns due to the dual CCDs of AEISS sensor. From the experiment we concluded that the third order polynomial-based RPCs update is required to minimize the sample direction image distortion. Finally we carried out the experiment on the epipolar resampling and the result showed the third order polynomial image transformation produced less than 0.7 pixels level of y-parallax.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.233-233
• /
• 2017

현재의 기술과 전문가들의 지식을 바탕으로 수치 예보 모델의 해상도가 점차 증가하고 있으나 한편으로는 해상도가 높아질수록 신뢰성 있는 장기 예보를 제공하는데 어려움이 있다. 즉, 고해상도 모델의 경우 미세한 오차가 발생 하더라도, 실제 기상학적 관점에서 시공간적으로 변동성이 크게 발생할 개연성이 크며, 이로 인해 모델에서 발생하는 불확실성은 더욱 커질 수 있다. 한국 기상청(KMA)에서는 영국기상청으로부터 도입한 통합모델(UM)을 현업 운영하고 있다. 본 연구에서 기상청 통합모델인 UM3.0 예보모델의 예측정확성을 다양한 관점에서 평가하고자 한다. 기상청 UM3.0 모델은 3km의 공간해상도와 1시간 시간해상도를 가지며, 예보시작시점기준 7일간의 예보정보를 제공한다. 강수량 예측정보의 활용성을 평가하기 위해서 예측 시계열에 대해 RMSE, 편의 및 등 다양한 통계지표와 공간적인 강수량 발생 특성을 평가하기 위해서 FSS 방법을 적용하였다. 본 연구 결과를 통해 UM3.0 모델의 1시간 및 3km의 시공간해상도와 선행예보 기간을 그대로 수문학적으로 활용하는 데에는 다소 무리가 있는 것으로 평가되었으며, 이러한 점에서 수문학적 활용관점에서 최적의 시공간적 규모와 선행예보 시간을 분석하였다.

• The Journal of Internal Korean Medicine
• /
• v.36 no.3
• /
• pp.348-360
• /
• 2015

Objectives From observing the tongue of a patient, one can assess the health status; this method has been frequently used in traditional Korean Medicine (KM) clinics. In particular, KM posits that the color of the tongue is highly related to digestive functions. In this study, the color of tongue and heart rate variability (HRV) were compared between chronic dyspepsia (CD) patients and healthy subjects. Methods Healthy subjects and CD patients with functional dyspepsia (FD), gastroesophageal reflux disease (GERD), or chronic gastritis (CG) were enrolled for the study. Profile view images of the tongue were acquired by using a computerized tongue image acquisition system (CTIS). The color of the tongue body was extracted from the non-coated region on the tongue images. Results Color differences in CIE L*a*b* color space between the three sub-types of CD patients and healthy subjects were analyzed by using multiple linear regression analysis with age and sex as the factors. The variable b* was significantly lower in GERD patients than in the controls (p=0.017). Variable a* was significantly lower in CG than in the controls (p=0.03). No significant difference was seen between FD and controls. In GERD, the tongue body seems to be intense red in color; in CG, pale red. Frequency domain analysis showed that HF was significantly lower in GERD patients than in the controls (p=0.041). Conclusions The color of the tongue body and HF of HRV can be used for diagnosing digestive functions in health care.

• Korean Journal of Remote Sensing
• /
• v.33 no.3
• /
• pp.333-338
• /
• 2017

We compared sea ice concentration(SIC) and sea ice extent(SIE) using EUMETSAT Ocean and Sea Ice Satellite Application Facilities(OSI SAF) and NASA Team(NT) sea ice algorithm in the Arctic during 1980-2010 to investigate the difference between sea ice data applied different algorithms. SIC and SIE of the two data showed different consistency by season and by sea area. Seasonally, SIC of OSI SAF was 0.85 % overall, 0.48 % in spring, 0.97 % in summer, 1.38 % in autumn and 0.66 % in winter higher than NT SIC. By sea area, OSI SAF SIC was 2.7 %, SIE was $198,000km^2$ higher than NT in Arctic Ocean, but in Lincoln Sea, OSI SAF SIC was 2.3 %, SIE was $20,000km^2$ lower than NT.

• Journal of Hydrogen and New Energy
• /
• v.11 no.1
• /
• pp.43-49
• /
• 2000

The heat transportation from a complex of industry to a rural area needs more efficient method because the distance between them is usually more than 10km. Conventional heat transportation using steam or hot water via pipe line has limits in transportation distance (about 3~5 km) because of the heat loss and frictional loss in the pipe line. Metal hydride can absorb or discharge hydrogen through exothermic or endothermic reaction. After releasing hydrogen from metal hydride by means of the waste heat from industry, we can transport this hydrogen to urban area via pipe line. In urban areas, other metal alloy reacts with this hydrogen to form metal hydride and produces heat for heating. Cool heat is also obtained if it is possible to use metal hydride with low reaction temperature. Therefore, metal hydride can be used as a media for transportation and storage of heat. $MmNi_{4.5}Al_{0.5}Zr_{0.003}$, $LaNi_5$, $Zr_{0.9}Ti_{0.1}Cr_{0.6}Fe_{1.4}$, $MmNi_{4.7}Al_{0.1}Fe_{0.1}V_{0.1}$ alloys were selected for this purpose and the properties of those metal hydrides were discussed. The design and control techniques were proposed and discussed for this heat transportation system using metal hydride.

• Journal of the Korean Society for Railway
• /
• v.13 no.3
• /
• pp.245-250
• /
• 2010

In this work, the stability and safety analysis are carried out to predict the performance of a next generation high-speed railway vehicle (HEMU-400X). Since the safety of the high-speed railway vehicles is very important, it is meaningful to predict the dynamic performance and stability of the railway vehicles using a numerical model at a railway vehicle design step. The critical speed of the dynamic model depending on the conicity of the wheel is calculated in the stability analysis. The critical speed calculated in this analysis is over 400km/h for the conicity value of 0.15, which is determined on the basis of representative international standard, UIC 518. Also, the lateral and vertical accelerations at several points of the same dynamic model are calculated for the safety analysis. In the simulation, the dynamic model runs at the test speed of 440km/h, which is determined considering a maximum target speed, and the total driving distance is 30km. And those estimated values are less than the allowed maximum acceleration values of UIC 518.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.8
• /
• pp.51-57
• /
• 2011

Surface water at the lower part of the Seom-jin river has a high salinity because the erosion at river bottom has made sea water move upstream continuously since 1978. The effect of underground dam on the prevention of sea water intrusion was modelled in this study. Present chloride concentration in surface water decreases exponentially along a river and in groundwater is about one-tenth of surface water's. The finite element method model, FEFLOW, was conducted on the assumption that the underground dam with a height of 25m over a bedrock is located under a water surface at the site of 4.6km from an estuary. The result shows that the position with chloride concentration of 0.25psu moves downstream from the sites of 25km to 22km, if an enough sedimentation with 5m thickness happens in the upper reservoir of underground dam. On the other side, the underground dam is little effective for the prevention of sea water intrusion in case of non-sedimentation.

• Journal of Korea Water Resources Association
• /
• v.42 no.7
• /
• pp.579-589
• /
• 2009

Hwang River in South Korea, has experienced channel adjustments due to dam construction. Hapcheon main dam and re-regulation dam. The reach below the re-regulation dam (45 km long) changed in flow regime, channel width, bed material distribution, vegetation expansion, and island formation after dam construction. The re-regulation dam dramatically reduced annual peak flow from 654.7 $m^3$/s to 126.3 $m^3$/s and trapped the annual 591 thousand $m^3$ of sediment load formerly delivered from the upper watershed since the completion of the dam in 1989. An analysis of a time series of aerial photographs taken in 1982, 1993, and 2004 showed that non-vegetated active channel width narrowed an average of 152 m (47% of 1982) and non-vegetated active channel area decreased an average of 6.6 km2 (44% of 1982) between 1982 and 2004, with most narrowing and decreasing occurring after dam construction. The effects of daily pulses of water from peak hydropower generation and sudden sluice gate operations are investigated downstream of Hapcheon Dam in South Korea. The study reach is 45 km long from the Hapcheon re-regulation Dam to the confluence with the Nakdong River. An analysis of a time series of aerial photographs taken in 1982, 1993, and 2004 showed that the non-vegetated active channel width narrowed an average of 152 m (47% reduction since 1982). The non-vegetated active channel area also decreased an average of 6.6 $km^2$ (44% reduction since 1982) between 1982 and 2004, with most changes occurring after dam construction. The average median bed material size increased from 1.07 mm in 1983 to 5.72 mm in 2003, and the bed slope of the reach decreased from 0.000943 in 1983 to 0.000847 in 2003. The riverbed vertical degradation is approximately 2.6 m for a distance of 20 km below the re-regulation dam. It is expected from the result of the unsteady sediment transport numerical model (GSTAR-1D) steady simulations that the thalweg elevation will reach a stable condition around 2020. The model also confirms the theoretical prediction that sediment transport rates from daily pulses and flood peaks are 21 % and 15 % higher than their respective averages.