• Journal of the Korea Convergence Society
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• v.4 no.3
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• pp.1-5
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• 2013

This study deals with simplified load calculation and structural testing for scale down model of small wind turbine blade. First, the blade was designed and produced scale down to 0.2 ratio of initial blade. And moments were acquired by simplified load calculation equations according to IEC 61400-2 standard. Also, structural test using weight was conducted to obtain the maximum moment. Therefore maximum moments were compared at calculation and test.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.32-41
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• 2009

In this study, scale-down design of full-scale Korean Utility Helicopter (KUH) main rotor blade has been investigated. The scaled model system were designed for the measurement of aerodynamic performance, tip vortex and noise source. For the purpose of considering the same aerodynamic loads, the Mach-scale method has been applied. The Mach-scaled model has the same tip Mach number, and it also has the same normalized frequencies. That is, the Mach-scaled model is analogous to full-scale model in the view point of aerodynamics and structural dynamics. Aerodynamic scale-down process could be completed just by adjusting scaling dimensions and increasing rotating speed. In the field of structural dynamics, design process could be finished by confirming the rotating frequencies of the designed blade with the stiffness and inertial properties distributions produced by sectional design. In this study, small-scaled blade sectional design were performed by applying domestic composite prepregs and structural dynamic characteristics of designed model has been investigated.

• Journal of the Korea Convergence Society
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• v.9 no.10
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• pp.1-6
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• 2018

This paper describes the azimuth accuracy of correlative interferometer direction finder on a scaled down airplane model. When the antennas are placed on the bottom of an airplane, reflection signals caused by an aircraft structure are arise and caused an azimuth error. In this paper, the F-16 fighter scale-down model was made to 5:1, and five antennas were placed on the bottom of the model. The accuracy was made by numerically analyzing the phases of the radio waves received by the five antennas when the signal of emitter was transmitted on $0-360^{\circ}$ azimuth angles. The azimuth error of the correlative interferometer direction finder on the model was measured to be less than $1.0^{\circ}$ when SNR was larger then 3dB, and it could be very useful for the design of the direction finder on airplane.

• Magazine of the Korea Concrete Institute
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• v.8 no.6
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• pp.183-193
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• 1996

The objective of this study is to investigate the characteristics of elastic and inelastic bekavior of ductile momenting-resisting reinforced concrete frame subjected to reversed lateral loading such as earthquake excitations. For this purpose, a 2-bay 2-story reinforced concrete plane frame with seismic detail was designed and one 1/2.5-scale subassemblage was manufactured according to the required similitude law. Then, the reversed load test under the displacement control was performed statically to this subassemblage. Finally, the results of this test were analysed regarding to (1) the design load vs actual strength, (2) degradation in stiffness and strength. (3) failure mode or energy dissipation. (4) local deformations.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.508-515
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• 2016

In this study, we compared the stability of the pillars by using room and pillar mining method with the four models with different stiffness and pillar overlap ratio. The experimental models consist of two plaster models (overlap ratio 0%, 100%) and two cement models(overlap ratio 0%, 100%). The soft and hard rocks are modeled by plaster and cement models respectively. In these experiments, the model materials with strength values reflecting the calculated scaled factors not been used, so it is not a true scaled model test that reproduces in situ state in the laboratory. Experimental results show that the different overlap ratio pillars are one of the factors that can affect the stability of the mine.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.3
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• pp.147-155
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• 2022

The accumulated ice and snow during the operation of aircraft and railway vehicles can degrade aerodynamic performance or damage the major components of vehicles. Therefore, it is crucial to predict the temporal growth of ice for operational safety. Numerical simulation of ice is widely used owing to the fact that it is economically cheaper and free from similarity problems compared to experimental methods. However, numerical simulation of ice generally divides the analysis into multi-step and assumes the quasi-steady assumption that considers every time step as steady state. Although this method enables efficient analysis, it has a disadvantage in that it cannot track continuous ice evolution. The purpose of this study is to construct a surrogate model that can predict the temporal evolution of ice shape using reduced-order modeling. Reduced-order modeling technique was validated for various ice shape generated under 100 different icing conditions, and the effect of the number of training data and the icing conditions on the prediction error of model was analyzed.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.249-250
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• 2022

최근 API Call을 기반으로 하는 악성코드 탐지 및 분류에 대한 연구가 활발히 진행되고 있다. 그러나 API Call 기반의 데이터는 방대한 양과 다양한 차원의 특성으로 인해 분석과 학습 모델 구축 측면에서 비효율적인 한계가 있다. 이에 본 연구에서는 방대한 API Call 정보를 포함하고 있는 CICAndMal2020 데이터 세트를 대상으로 기존의 특성 선택 기법이 아닌 주성분 분석(Principal Component Analysis)을 사용하여 차원을 대폭 축소 시킨 후 머신러닝 기법을 적용하여 분류를 시도하였다. 실험 결과 전체 9,503개의 특성을 25개의 주성분(전체 대비 약 0.26% 수준)으로 축소시키고 다중 분류 기준 약 84%의 정확도를 나타냈다. 결과적으로 기존 연구에서의 탐지 모델 대비 정확도, F1-score 등의 성능 향상은 물론 차원 축소 측면에서 매우 향상된 결과를 달성하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.357-360
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• 2007

NREL Phase VI 12% 축소모델을 사용한 표준풍력터빈 풍동시험은 2006년에 1차 시험이 수행되었다. 1차 풍동시험은 복합재 블레이드를 사용하여 표준조건(설치각 3도)에 대해 수행되었으며 블레이드 표면상태에 따라 측정값이 영향을 받는 것을 파악하였다. 2007년 4월에 수행된 2차 풍동시험은 표면상태의 영향을 보다 정확히 파악하기 위해 알루미늄 블레이드를 사용하여 시험을 수행하였으며, 블레이드 제작 정밀도에 따른 영향을 파악하였다. 낮은 레이놀즈 수 영역(저속영역)에서는 블레이드 표면상태 따라 토크 값 다르게 나타나며, 블레이드 끝단 부근의 제작 정밀도는 최대 토크 이후의 영역에 영향을 미치는 것으로 나타났다. 0.1mm 이내의 정밀도로 제작된 모델의 경우 NREL 시험결과와 전체적인 형상이 유사하게 나타나며, 축소효과에 의한 영향으로 최대토크는 약 25% 정도 감소현상을 보이고 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.988-992
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• 2007

Recently, dynamic system has been enlarged and is exposed to various types of disturbance. Thus designing controller for those dynamic system under random disturbance is not practically easy. As a result, the exact analysis for the system which is exposed to various irregular disturbance is quite important. In order to perform analysis, conventional BMR(Balanced Model Reduction) method is applied to moment equation in stochastic domain and reliable reduced order system model has been obtained.

• Journal of Korea Water Resources Association
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• v.30 no.3
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• pp.201-210
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• 1997

To analyze the flow through open-channel constrictions using $\kappa$-$\varepsilon$ turbulence mode, a numerical model is developed. The simulated results agree well with existing experimental data which attributes to the adequate input of turbulent eddy-viscosity by turbulence model. A stream function and velocity distributions enable the analysis of flow characteristics at the downstream of constriction. Turbulent eddy viscosities over channel are spatially varied with stream pattern. For the evaluation of rapidly varied flow, the eddy-viscosity input by turbulence model is required instead of the empirical effective viscosity to solve a shallow water equation.