• Journal of Korea Water Resources Association
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• v.33 no.1
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• pp.87-98
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• 2000

The objective of this study is to test the flood forecasting capability of TOPMODEL on a single watershed in Korea. The selected study area is the Soyang River basin with outlet at Soyang Dam site. The three daily hydrographs and the three hourly flood events during 1990~1996 are selected for model calibrations and performance tests. The model parameters are estimated on 1990 daily event by manual fitting technique and the effects of topographic index distribution to river flow simulations are investigated on the study area. The model performance on correlation coefficient between the observed and the simulated flows for the verification periods are above 0.77 on the 95-, 96-daily events, while above 0.87 for 90-, 95-, 96-hourly events. By the consideration of flood flow characteristics in Korea, the physical interpretation of the model concept, and the model performance, it can be concluded that the TOPMODEL is feasible as a flood forecasting model in Korea. Korea.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1078-1084
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• 2010

The tracking performance of a big parabola tracking antenna system for tracking and receiving of the signal from the vehicle is impacted by many factors of the internal and the external of the system. In this paper, we analyze the tracking error due to the radio refraction in the application of the tracking and positioning of the vehicle by using radio frequency. The real measurement data are used for the analysis which had been acquired by using GPS and the tracking systems of C- and S-band frequencies in NARO Space centre. To verify the correlation between the tracking errors measured and the radio refraction, we review the error factors and the accuracies of the tracking systems, and the characteristics of the refractivity. The analysis shows that there are angular errors which are due to the radio refraction and not to be neglected, compared to the accuracies of the tracking systems, in case of low elevation angle less than 10 degrees. Also, the tracking errors depend on the target altitude as well as the elevation angle for the case of the target in the troposphere. It is recommended to correct the tracking angle considering the target altitude and elevation angle for the precise target positioning.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.527-533
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• 2015

This study performed an on-site demonstration of the topographic surveying technique at a large-scale open-pit limestone mine in Korea using a fixed-wing unmanned aerial vehicle (UAV, Drone, SenseFly eBee). 288 sheets of aerial photos were taken by an automatic flight for 30 minutes under conditions of 300 m altitude and 12 m/s speed. Except for 37 aerial photos in which no keypoint was detected, 251 aerial photos were utilized for data processing including correction and matching, then an orthomosaic image and digital surface model with 7 cm grid spacing could be generated. A comparison of the X, Y, Z-coordinates of 4 ground control points measured by differential global positioning system and those determined by fixed-wing UAV photogrammetry revealed that the root mean squared errors were around 15 cm. Because the fixed-wing UAV has relatively longer flight time and larger coverage area than rotary-wing UAVs, it can be effectively utilized in large-scale open-pit mines as a topographic surveying tool.

• Journal of Korea Water Resources Association
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• v.34 no.3
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• pp.241-251
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• 2001

A flow determination algorithm is proposed for the distributed hydrologic model. The advantages of a single flow direction scheme and multiple flow direction schemes are selectively considered to address the drawbacks of existing algorithms. A spatially varied flow apportioning factor is introduced in order to accommodate the accumulated area from upslope cells. The channel initiation threshold area(CIT) concept is expanded and integrated into the spatially distributed flow apportioning algorithm in order to delineate a realistic channel network. An application of a field example suggests that the linearly distributed flow apportioning scheme provides some advantages over existing approaches, such as the relaxation of over-dissipation problems near channel cells, the connectivity feature of river cells, the continuity of saturated areas and the negligence of the optimization of few parameters in existing algorithms. The effects of grid sizes are explored spatially as well as statistically.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.75-81
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• 2002

In the re-entry comtrol system, errors apt to induce because the time deriviative of drag acceleration is analytically estimated. Still more, the difficulty of estimation of th exact drag coefficient in hypersonic velocity and the non-reality of the scale height cause a steady-state drag errer. In the Space-Shuttle, a steady-state drag error is reduced by the addition of the integral term of drag acceleation error into the control system. This method, however, induces a difficulties in respect to the modern controller composition due to the multi-poles in a closed-loop system. Thus, this paper proposes the additional method of the disturbance observer. This reduces the steady-state drag error according to the following by the analytic calculation, and then creates the new drag acceleration time derivative using the estimated error. The performance of the re-entry control system is verified about 32 refernce trajectories.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.11
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• pp.1123-1129
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• 2010

Angular Deviation(AD) on transparency applied to TA-50 Aircraft deteriorates armament system's accuracy because it makes a difference in between actual and theoretical targets. In order to increase accuracy, therefore, TA-50 Aircraft measures AD on transparency and provide the measured values for the integrated mission display computer as a type of AD coefficients. This makes AD revised so that pilots can accurately see the actual target on their head-up display. In order to implement such mechanism into a real field, we develop a new device and system automatically measuring AD for the first time. We also deal with basic concept including AD induction formula as well as operating systems. As a consequence of testing the accuracy and precision for verifying reliability of the system, we got satisfactory results. In specific, the accuracy was within the resultant criterion of 1%. The precision was also satisfied with respect to the whole criteria. The system developed through this research is qualified as a military standard equipment for transparency of the canopy.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.18-28
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• 2016

Numerical analysis was conducted as a preliminary study for evaluating the dual bell nozzle. For future parametric studies, a dual bell nozzle was designed, and thereafter inlet condition, turbulence model, and the number of optimum grids were determined. Dual bell nozzle was designed based on the KSLV-II first stage nozzle. Inlet condition was determined to frozen flow model of non-reacting eight species by comparing with the design values. SST $k-{\omega}$ model turned out to be suitable as turbulence model. About 150 thousand of the grids were selected after grid sensitivity tests. Based on the results determined in this study, we plan to investigate performance gain of the KSLV-II by adopting a proposed dual bell nozzle.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.229.2-229.2
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• 2012

지금까지 해외의 여러 달 궤도선에서 달의 영상을 다양한 방법으로 관측한 것에서 알 수 있듯이 영상 관측은 달 탐사에서 중요한 부분이다. 특히 그 중에서 입체 영사기(Stereo Imager)는 달의 3차원적 영상을 관측하여 달 표면의 구조를 파악할 수 있고 분광 카메라(Hyperspectral Camera)는 달 표면을 이루고 있는 물질을 분광 정보를 통해서 알아낼 수 있다. 본 연구에서는 우리나라가 2020년경 독자적인 달 궤도선을 계획하고 있는 것에 발맞추어 이 두 관측 장비를 설계해 보았다. 본 연구에서 설계한 탑재체는 하나의 광학계를 이용해 가시광 영역에서 동시에 입체 영상과 분광 영상을 얻을 수 있는 장치이며, 달 표면에서의 궤도선의 속도와 저장 가능한 정보의 양을 고려하여 100 km의 고도에서 속도를 1.6 km/s로 가정할 때 interline CCD가 17.5 m의 공간 분해능을 갖기 위해 92 frame/s 이상의 frame rate로 관측을 수행할 수 있게 하였다. 특히 분광 카메라는 wedge filter를 사용하여 광학계의 부담을 줄였으며 검출기로는 interline CCD를 사용하여 channel 수를 조절할 수 있도록 하였다. 또한 달 표면을 구성하는 입자의 크기에 대한 정보를 얻을 수 있는 편광판도 설치 하였다. 시험 모델의 문제점을 분석하여 새롭게 개선된 탑재체를 설계하여 개발하였다. 렌즈를 수정해 vignetting과 왜곡 현상을 보정하였고 전체 무게를 1.5 kg으로 줄여서 시험 모델보다 30% 이상 줄일 수 있었다. 파장 분해능은 20nm로 시험모델보다 더 개선된 분해능을 얻을 수 있었다. 출력 효율의 증대를 위해 power board의 수정을 수행하였다.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.5
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• pp.31-39
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• 2020

According to lessons learned from an accident of Fukushima Daiichi nuclear power plant, it is advisable to make a comprehensive radiation survey by the accident phase for efficient response and risk management using diverse survey platforms. This study focuses on the technical status of environmental radiation monitoring using a UAV (Unmanned aerial vehicle) and the performance test of developed aerial survey system based on two detectors with an high energy resolution through the field application to contaminated areas. Finally, the performance of aerial survey at diverse flight heights was successfully achieved by introducing the correction factor to represent the results into ambient dose rate at 1m above the ground.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.413-413
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• 2018

최근 도시지역에 태풍과 집중호우로 인한 홍수발생 빈도와 그 규모가 커지고 있다. 이에 따른 재산 및 인명피해 양상도 매우 심각한 상황이다. 태풍 차바 처럼 강력한 10월 태풍의 출현은 지구 온난화의 전조로 받아들여지고 있다. 또한 10월 태풍임에도 초속 56.5m의 순간 최대풍속과 시간당 최대 116.7mm(제주 서귀포), 139mm(매곡) 등의 강수량은 지역 최대 강수량을 기록함으로써 이제 언제나 태풍 및 홍수에 대한 대비가 필요하게 되었다. 현재 재해에 대비하기 위해 다양한 대책들은 꾸준히 마련되어지고 있으며, 설계 기준 또한 강화되었다. 그러나 저류조 및 배수펌프장 등의 시설물 설치에는 막대한 예산이 필요한데다 장기간의 시간이 필요하며, 비구조적 대책도 마련되어 있으나 태풍 차바의 사례에서 경험한 것처럼 재해 발생 시 대책과 구체적인 방안의 마련이 더욱 시급해 보인다. 이에 본 연구에서는 태풍 차바 시의 호우에 대하여 UNET모형에 의한 부정류모의를 수행하였다. 부정류모의의 경계조건으로써 상류단 경계조건과 측방유입량 조건은 HEC-HMS를 이용하여 유출해석을 실시한 다음 입력 자료로 이용하였으며, 하류단 경계조건으로는 국토부 관할 수위지점의 수위를 이용하여 UNET 모형에 의한 수리학적 하도추적을 수행하였으며, 저지대 침수분석은 지형정보시스템 응용프로그램 중 하나인 ArcGIS를 활용하여 대상유역의 벡터자료를 구축하고 인접도엽의 접합 및 보정을 실시하여 수치고도자료를 생성하여 2차원 홍수범람해석을 위한 HEC-RAS 5.0을 적용하여 침수분석을 수행하였다. 본 연구의 결과를 수재해 피해저감 대책을 수립하는데 기초자료로 활용될 수 있을거라 판단된다.