• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.33.1-33.1
• /
• 2011

풍력발전기가 점차 대형화되어가는 추세에 따라 블레이드 역시 점차 길어지고 무거워지는 경향을 보이고 있다. 이는 블레이드뿐만 아니라 풍력발전기 시스템 전체의 하중 및 비용의 증가를 불러오게 되므로, 시스템의 성능 및 하중에 가장 큰 영향을 끼치는 블레이드의 공력특성에 대한 연구가 전 세계적으로 지속되고 있다. 그 중에서도 특히 작동 중 오염에 의한 블레이드 표면 거칠기 변화는 블레이드의 공력특성을 변화시켜, 발전기 전체의 성능뿐만 아니라 전체 하중에도 영향을 끼치는 주요 인자이다. 따라서 풍력발전기 블레이드 설계 시에 예측된 설계하중과 실제 운용 환경에 의해 변화된 운용하중 간의 차이를 예측할 수 있다면, 블레이드 설계 시에 표면 거칠기 변화에 따른 영향을 고려함으로써 실제 운용 환경에 맞는 최적의 블레이드 및 풍력발전기 시스템 설계를 수행할 수 있다. 본 연구에서는 블레이드의 표면 거칠기 변화에 따라 풍력발전기 하중이 어떻게 영향을 받는지에 대하여 분석하였다. 이를 위하여 표면 거칠기 민감도를 고려하지 않고 설계된 기준 블레이드와, 운용 중 표면 거칠기가 변화된 블레이드의 2개 모델에 대한 하중해석을 수행하고 그 결과를 비교하였다. 보다 실제적인 해석을 위해 Multi-MW 급 풍력발전기 시스템 모델을 대상으로 최적 설계된 블레이드를 기준 모델로 삼았다. 하중계산방법은 IEC 및 GL 2010 가이드라인을 참고하였으며, 일부 주요 극한하중 상황에 대하여 해석을 수행하여 설계하중상황(design load case, DLC) 별로 하중의 증감 및 경향을 비교하였다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2022.05a
• /
• pp.18-20
• /
• 2022

3D 프린팅 임플란트 부품은 표면에 결함이 생기기 쉬우므로, 출력 후 표면을 검사하는 과정이 필요하다. 표면 검사를 자동화하기 위해서는 임플란트를 3D 스캔하여 점군 (point cloud)와 같은 스캔 모델로 구성하는 방법이 효과적이다. 스캔 모델을 구성할 때, 임플란트가 일반적인 3D 프린팅 출력물과는 다른 특성들을 가지므로 이에 대한 고려가 필요하다. 본 논문에서는 3D 프린터로 출력된 의료용 임플란트 부품의 특성에 맞게 3D 스캔을 수행하여 스캔 모델을 구성하는 방법을 제안하고, 실험을 통해 생성된 스캔 모델을 보인다.

• Journal of the Korea Concrete Institute
• /
• v.26 no.1
• /
• pp.79-86
• /
• 2014

In this paper, a stress transfer mechanism between near surface-mounted (NSM) fiber reinforced polymer (FRP) plate and concrete was investigated and a reliable analytical procedure for it was presented by using bilinear bond-slip model simulating the bond behavior of NSM FRP plate. As a result, critical values in the bi-linear model such as maximum shear strength, slip at that time and failure slip at the initiation of softening de-bonding were suggested for being used in the differential equation considering he interfacial characteristic between NSM FRP and concrete. Also, it was found that the bond-slip behavior could be suitably redicted by using the proposed procedure even in the case of various bond lengths from the comparison with bond test result.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.3
• /
• pp.1630-1638
• /
• 2015

The finite element analysis has become an essential process to investigate the structural performance in many industry fields. In addition, the computer's performance is improving rapidly, but in large design problems, there is a limit to apply the optimal design techniques. For this, it is general to introduce a metamodel based optimization technique. The method to generate an approximate model can be classified into curve fitting and interpolation, and each representative one is response surface model and kriging interpolation method. This study proposes an ensemble model made of RSM and kriging to solve a structural design problem. The suggested method is applied to the designs of two bar and automobile outer tie rod.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.7
• /
• pp.723-733
• /
• 2011

A numerical method of the CSF(Continuum Surface Force) model is presented for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The application of the present method to a 2-D liquid drop problem is illustrated by an equilibrium and nonequilibrium oscillating drop calculation. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.4 no.3
• /
• pp.296-300
• /
• 2003

A large equilibrium and kinetic data set for multi-component cation exchanges was obtained and tested with mass action law and surface complexation model. The systematic batch equilibrium and column experiments of cation adsorption were conducted for binary, ternary, quaternary, and quinary cation exchanges involving $ H^{+}, Li^ {+}, Na^{+}, NH$_4$^{+}, Mg^{2+} $ on a strongly acidic cation exchange resin IRN 77. The mass action law and surface complexation model were tested against both data set to investigate the consistency of ion selectivity and their predictability for competitive cation exchanges. Surface complexation model provided more accurate predictions for both equilibrium and kinetic experimental data than mass action model.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2009.10a
• /
• pp.233-234
• /
• 2009

증착된 silicon nitride (Sin) 박막의 수명 시간을 예측하는 신경망 모델을 개발하였다. SiN 박막은 플라즈마 화학기상 증착방식을 이용하여 증착되었다. 증착 공정은 통계적인 실험계획표를 이용하여 수행되었고, 신경망 모델의 예측 성능은 유전자 알고리즘을 이용하여 최적화하였다. 수명시간은 다른 박막특성 (굴절률, 증착률, 전하밀도)의 영향을 상당히 받았으며, 특히 굴절률과 전하밀도는 높은 증착률에서 증가시킬 때 수명시간을 최대화할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.5
• /
• pp.772-780
• /
• 1987

The normal and tangential belt forces for two types of flat belts are measured and compared. From friction theory, ti was assumed that tangential friction is proportional to the actual contact area $A_{a}$ and $A_{a}$ is proportional to normal pressure P; i.e., $A_{a}$ .var.P$^{n}$ . For a flat belt with cloth backing, the n=2/3 is obtained for the constant of belt surface model. For a flat belt with rubber backing, the n=0.9 to n=1.0 is suggested as a surface model constant. The theoretical equation developed in this paper showed agood with the experimental results.

• Korean Journal of Remote Sensing
• /
• v.28 no.5
• /
• pp.549-559
• /
• 2012

This paper presents a comparative analysis on the applicability of a priori statistic information about adjustment models when the surface shape parameters are estimated at an arbitrary point in an elevation data. Although the reliability of the estimates are known to be affected by surface condition and the adjustment models, there has been little research in a systematic and detail way. When the raw data have been taken from a real measurement, its true value cannot be known, however, thus this study used simulation data in order to analyze clearly the applicability of adjustment models. The generation of simulated data was performed by superimposing horizontal, slope, and curve surfaces and adding a certain amount of noise. Comparative analysis was performed by associating the a posteriori estimates with a priori statistics of each adjustment models. The experimental results show the estimation characteristics of adjustment models against varying surface conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.17 no.12 s.115
• /
• pp.1172-1180
• /
• 2006

The backscattering coefficients of a bare soil surface were measured using an R-band polarimetric scatterometer, which were used to verify the validities of scattering models and inversion algorithms. The soil moisture contents and the surface roughness parameters (the RMS height and correlation length) were also measured from the soil surface. The backscattering coefficients were obtained from several scattering models with these surface parameters, and the computation results were compared with the measured backscattering coefficients. The soil moisture contents of the surface were retrieved from the measured backscattering coefficients, and compared with the measured surface parameters. This paper shows how well the scattering models agree with the measurements, and also shows the inversion results.