• 한국농공학회지
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• 제29권2호
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• pp.53-63
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• 1987

Due to their wide range of application, deterministic comprehensive hydrologic models using digital computers have been developed in all countries of the world and researches are being undertaken for their appropriate applications. The aim of this study has been to demonstrate the practical implementation of a physically based distributed hydrologic model, the USDAHL-74 model and to investigate its ability to simulate the long term estimate of water balance quantities in a Korean mountainous watershed. Application of the model to Dochuk watershed indicates the following results. 1.Since the USDAHL-74 model includes all the major components of the hydrologic cycle in agricultural watersheds, thus is comprehnsive, the model seems to have a wide range of application from the fact that simulation results obtained are not only runoff volumes m various time units but their spatial variation as well as even soil moisture within the watershed. 2.An approximate calibration to determine the parameter values in the model using various data obtained from D0chuk shed shows that the simulation error of yearly runoff volume is only 0.6 % and a correlation coefficient between observed daily runoff volume and simulated one is 0.91 in all calibrated period.3.As a verification test of the model, runoff volumes are simulated using 1986 year data without changing the parameter values determined by 1985 year data. The tests show that the USDAHL-74 model is a flexible tool and that realistic production to simulate the long term estimate of runoff in Korean mountainous watershed could be obtained using only a short period of calibration.4. Despite of the encouraging results, there still remain minor problems concerning the practical application of the model to improve the result of simulations. Some of these are the small descrepancies between observed and simulated daily runoff volume appeared in the vicinity of peaks and the recession of1 the daily hydrographs and the model performance for the frozen ground and melting process in the model. 5. Alough the use of parameter with physical significance and the ability to improve calibrations on the basis of physical reasoning represents advantages in the simulation for ungaged watersheds, further researches are needed to use the USDAHL-74 mode to simulate runoff in ungaged watersheds.

• 제어로봇시스템학회논문지
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• 제21권8호
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• pp.753-757
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• 2015

This paper introduces an experimental rescue robot, HUBO T-100 and presents the optimal motion control method. The objective of the rescue robot is to extract patients or wounded soldiers in the battlefield and hazardous environments. Another mission is to dispose and transport an explosive ordnance to safe places. To execute these missions, the upper body of the rescue robot is humanoid in form to execute various kinds of tasks. The lower body features a hybrid tracked/legged design, which allows for a variety of mode of locomotion, depending on terrain conditions in order to increase traversability. The weight lifting motion is one of the most important task for performing rescue related missions because the robot must lift an object or impaired person lying on the ground for transferring. Here, dynamics based motion optimization is employed to minimize joint torques while maintaining stability simultaneously. Physical experiments with a real humanoid robot, HUBO T-100, are presented to verify the proposed method.

• 한국정보통신학회논문지
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• 제20권10호
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• pp.1860-1866
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• 2016

헬기 사고의 대부분은 시야가 제한된 상황에서 착륙 시 구조물과의 충돌에 의한 사고로 안전한 주행을 위해 레이더와 같은 보조 장비가 요구된다. 본 논문에서는 회전하는 안테나를 장착한 헬기 레이더가 착륙하는 과정에서 고정 클러터에 대한 거리-방위각 이미지를 얻는 알고리즘을 제시한다. 동일 거리에 위치한 각각의 클러터 패치로부터 수신되는 신호를 모델링하고 클러터 특성 및 도플러 특성을 분석한다. 부엽(side lobe) 성분을 억제하고 주 빔(main lobe) 신호성분을 얻기 위한 필터구조를 설계하고 이 과정에서 발생하는 문제점에 대한 해결책을 제시한다. 마지막으로 시뮬레이션에 의해 거리-방위각 도메인에서의 가상의 지형 시나리오를 생성한 후 제시한 알고리즘의 성능을 검증한다.

• Steel and Composite Structures
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• 제28권2호
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• pp.223-231
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• 2018

Nowadays, there are a great number of various structures that have been retrofitted by using different FRP Composites. Due to this, more researches need to be conducted to know more the characteristics of these structures, not only that but also a comparison among them before and after the retrofitting is needed. In this research, a model steel structure is tested using a bench-scale earthquake simulator on the shake table, using recorded micro tremor data, in order to get the dynamic behaviors. Columns of the model steel structure are then retrofitted by using GFRP composite, and then tested on the Quanser shake table by using the recorded micro tremor data. At this stage, it is needed to evaluate the dynamic behaviors of the retrofitted model steel structure. Various types of methods of OMA, such as EFDD, SSI, etc. are used to take action in the ambient responses. Having a purpose to learn more about the effects of GFRP composite, experimental model analysis of both types (retrofitted and no-retrofitted models) is conducted to evaluate their dynamic behaviors. There is a provision of ambient excitation to the shake table by using recorded micro tremor ambient vibration data on ground level. Furthermore, the Enhanced Frequency Domain Decomposition is used through output-only modal identification. At the end of this study, moderate correlation is obtained between mode shapes, periods and damping ratios. The aim of this research is to show and determine the effects of GFRP Composite implementation on structural responses of the model steel structure, in terms of changing its dynamical behaviors. The frequencies for model steel structure and the retrofitted model steel structure are shown to be 33.916% in average difference. Finally, it is shown that, in order to evaluate the period and rigidity of retrofitted structures, OMA might be used.

• Smart Structures and Systems
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• 제25권1호
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• pp.81-96
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• 2020

Wind measurements were made on the Canton Tower at a height of 461 m above ground during the Typhoon Vincente, the wind-induced accelerations and displacements of the tower were recorded as well. Comparisons of measured wind parameters at upper level of atmospheric boundary layer with those adopted in wind tunnel testing were presented. The measured turbulence intensity can be smaller than the design value, indicating that the wind tunnel testing may underestimate the crosswind structural responses for certain lock-in velocity range of vortex shedding. Analyses of peak factors and power spectral density for acceleration response shows that the crosswind responses are a combination of gust-induced buffeting and vortex-induced vibrations in the certain range of wind directions. The identified modal frequencies and mode shapes from acceleration data are found to be in good agreement with existing experimental results and the prediction from the finite element model. The damping ratios increase with amplitude of vibration or equivalently wind velocity which may be attributed to aerodynamic damping. In addition, the natural frequencies determined from the measured displacement are very close to those determined from the acceleration data for the first two modes. Finally, the relation between displacement responses and wind speed/direction was investigated.

• Earthquakes and Structures
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• 제8권4호
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• pp.889-913
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• 2015

Structural vibration characteristics of a semi-active base-isolated building were investigated using seismic observation records including those of the 2011 Great East Japan earthquake (Tohoku earthquake). Three different types of analyses were conducted. First, we investigated the long-term changes in the natural frequencies and damping factors by using an ARX model and confirmed that the natural frequency of the superstructure decreased slightly after the main shock of the Tohoku earthquake. Second, we investigated short-term changes in the natural frequencies and damping factors during the main shock by using the N4SID method and observed different transition characteristics between the first and second modes. In the second mode, in which the superstructure response is most significant, the natural frequency changed depending on the response amplitude. In addition, at the beginning of the ground motion, the identified first natural frequency was high possibly as a result of sliding friction. Third, we compared the natural frequencies and damping factors between the conditions of a properly functional semi-active control system and a nonfunctional system, by using the records of the aftershocks of the Tohoku earthquake. However, we could not detect major differences because the response was probably influenced by sliding friction, which had a more significant effect on damping characteristics than did the semi-active dampers.

• 한국지반공학회논문집
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• 제18권5호
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• pp.55-65
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• 2002

소성흐름을 발생시키는 측방유동 가능지반내에 설치된 매설관에 작용하는 토압에 대한 메카니즘을 규명하기 위해 파괴형상실험을 실시하고, 파괴형상실험을 토대로 지반변형속도를 고려하기 위해 Maxwell 점탄성 모델을 적용한 토압산정식을 제안하였다. 직접전단실험으로 구한 점성계수와 내부마찰각과 상재압을 고정하여 이론식으로 도출해낸 점성계수가 잘 일치하고 있음을 확인하였고 모형실험결과와 이론식에 의한 토압은 지반변형속도에 영향을 받으며 비교적 일치하며 지반변형이 없는 경우에도 정지토압을 받음을 알 수 있다. 또한, 지반의 지지력은 점성토에서는 관입전단파괴시의 값과 거의 일치하였다. 또한, 매설관 주변지반의 파괴모드는 매설관직경과 무관하게 지반변형속도에 영향을 받으며 작용토압은 균질한 지층의 경우 선형적으로 증가하고 조립질에 가까울수록 선형적 감소치를 보이므로 매설관주변지반의 매립재를 이용하여 매설관주변의 토압을 경감시킬 수 있음을 알 수 있다.

• International Journal of Aeronautical and Space Sciences
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• 제13권1호
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• pp.117-125
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• 2012

This paper presented the design of SRPS, ground function test, and the deployment test on a high speed taxi of KC-100 airplane. KAI has developed a spin recovery system in collaboration with Airborne Systems for KC-100 general aviation airplane. Spin mode analysis, rotary balance and forced oscillation tests were performed to obtain the rotational, dynamic derivatives in the preliminary design phase. Prior to the detailed design process of SRPS, approximations for initial estimation of design parameters- fineness ratio, parachute porosity, parachute canopy filling time, and deployment method- were considered. They were done based on the analytical disciplines such as aerodynamics, structures, and stability & control. SRPS consists of parachute, tractor rocket assembly for deployment, attach release mechanism (ARM) and cockpit control system. Before the installation of SRPS in KC-100 airplane, all the control functions of this system were demonstrated by using SBTB(System Breakout Test Box) in the laboratory. SBTB was used to confirm if it can detect faults, and simulate the firing of pyrotechnic devices that control the deployment and jettison of SRPS. Once confirmed normal operation of SRPS, deployment and jettison of parachute on the high speed taxiing were performed.

• 펄프종이기술
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• 제44권4호
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• pp.16-24
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• 2012

To characterize the coating structure, diverse methods such as mercury intrusion, nitrogen adsorption and oil absorption methods have been developed and widely employed. These indirect techniques, however, have some limitation to explain the actual coating structure. Recently microscopic observation methods have been tried for analyzing structural characteristics of coating layers. Preparation of the undamaged cross section of a coating layer is essential for obtaining high quality image for analysis. In this study, distortion-free cross-section of the coating layer was prepared using a grinding and polishing technique. The coated paper was embedded in epoxy resin and cured. After curing the resin block it was ground with abrasive papers and then polished with diamond particle suspension and nylon cloth. Polished coating layer was sufficient enough to obtain undamaged cross sectional images with scanning electron microscope under backscattered electron image mode. In addition, the SEM images allowed distinction of the coating layer components. Also S/B latex film formed between pigment particles was visualized by osmium tetroxide staining. Pore size distribution and pore orientation were evaluated by image analysis from SEM cross-sectional images.

• 대한원격탐사학회지
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• 제16권1호
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• pp.73-86
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• 2000

Pushbroom위성 영상의 카메라 모델링을 위한 대표적 방법들을 구현하고 성능을 분석하였다. 구현된 모델들은 벡터 진행 모델, Gugan and Dowman(GD)의 모델, 상용 소프트웨어의 근간을 이루는 Orun and Natarajan(ON)의 모델, Direct Linear Transformation(DLT)모델이다. 서울/경기지역 의 SPOT 영상에 대해 지상기준점의 수를 1개에서 23개까지 변화하면서 카메라 모델을 수립하였다. 지상기준점이 6개 미만인 경우에는 벡터 진행 모델이 최고 2.7픽셀의 정확도를 보인 반면 이외의 모델들은 사용할 수 없다. 6개 이상인 경우에는 ON모델이 최고 1픽셀의 정확도로 가장 우수한 성능을 보인다. 이때 벡터 진행 모델은 최고 1.5픽셀의 정확도를 갖는다. GD모델은 모델 변수간의 상관관계로 인하여 대부분의 경우 모델 수립에 실패하였다. DLT모델의 정확도는 특정 지상기준점의 포함여부에 따라 1∼4픽셀 사이에서 진동한다. 모델링의 부산물로서 벡터 진행 모델은 위성궤도 추정에 응용할 수 있는 장점이 있다 향후 연구 과제로는 위에서 열거한 정확도로부터 지상기준점에 내재한 오차 제거, 벡터 진행 모델의 성능 향상 등이 있다.