• Korean Journal of Environment and Ecology
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• v.21 no.6
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• pp.536-543
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• 2007

This research was conducted every month from June 1994 until August 1996 with the aim to understand the ecosystem structure through the analysis of oribatid mite community structure in soil subsequent to environmental difference of its habitats located at northward & southward slopes adjacent to each other at an altitude of 1,000 meters of Mt.Jumbong, which is a natural reserved forest, remaining intact. There appeared a significant difference [t-test, p<0.06] in comparison of the number of the species and individuals of Oribatid mite species which were collected and identified at two survey areas. The mean density and the number of the species collected and identified at the northward slopes, and southward slopes were $99.2{\pm}17.6,\;234.2{\pm}62.6$ and $24.7{\pm}3.0,\;40.8{\pm}5.8$, respectively. Species diversity index(H') was higher at the southward slopes($3.09{\pm}0.11$) than at the northward slopes($2.71{\pm}0.13$). The population size of Oribatid mite species was found by the percentage of each species density as against the whole density and classified into dominant species, influent species, and recessive species according to the percentage; as a result, O. nova and Suctobelbella naginata was found to be a dominant species at both survey slopes while Trichogalumna nipponica was found to be a dominant species, at southward but it wasn't collected at the northward slopes at all. The feeding habit of the dominant species at two survey slopes was found to be microphytophagous- eating soil microbe. There appeared a conspicuous difference in compositions of the number of the species, individuals and dominant species at the southward/northward slopes adjoining each other at an attitude of 1,000 meters and less similarity between the two survey slopes. Conclusively, It was found that the heterogeneity of microhabitat has a great effect on Oribatid mite's community characteristics.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.295-300
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• 2005

The freeplay, one of the concentrated structural nonlinearities, is inevitable for control surfaces of a real air vehicle due to normal wear of components and manufacturing mismatches. Also aerodynamic nonlinearities caused by a shock wave occur in transonic region. In practice, these nonlinearities induce the limit cycle oscillation (LCO) and decrease the transonic flutter speed. In this study, the fictitious mass method is used to apply a modal approach to nonlinear structural models due to freeplay. The transonic small-disturbance (TSD) equation is used to calculate unsteady aerodynamic forces in transonic region. Nonlinear aeroelastic time responses are predicted by the coupled time integration method (CTIM). This method was also applied to a 3D all-movable control wing to investigate its nonlinear aeroelastic responses. The angle of attack effect on the LCO characteristics has been found to be closely related with the initial pitching moment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.500-503
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• 2009

본 논문에서는 이중곡률을 갖은 막구조물의 동적 불안정 현상을 연구하였다. 풍하중을 받는 막구조물의 지배방정식을 정식화할 경우 가장 중요한 것은 막 표면의 공기 압력을 합리적으로 산정하는 것이다. 베르누이 윈리에 의하여 유체 압력은 속도 퍼텐셜과 관계를 가지며 얇은 날개 원리에 의해 막 표면 공기의 움직임을 일련의 와류로 간주하고 속도 퍼텐셜을 구할 수 있다. 이 논문에서는 가장 많이 쓰이는 3 절점 삼각형 막요소를 이용하여 가중 잔여치 갤러킨법을 적용한 안정 평가의 판별식을 유도하였다. 임계 풍속에 대한 초기인장력, 풍방향과 곡률의 영향도 분석하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.151-154
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• 2009

본 연구에서는 Proper Orthogonal Decomposition (POD)를 이용하여 공력축소모델을 구축하였다. 일반적으로 Euler equations과 같은 높은 정확도를 가지는 공력해석을 수행할 경우 많은 계산 비용이 발생하게 된다. 특히 공탄성 해석과 같이 수차례의 공력해석이 필요한 경우 그 비용은 더 증가하게 된다. 이러한 문제를 줄이기 위해서 축소모델(Reduced Order Model; ROM)의 개발은 반드시 필요하다. 공력축소모델을 구하는 방법 중 하나인 POD는 snapshot 데이터로부터 기저벡터를 구하고, 이들의 선형결합을 통하여 축소된 공간에서 해를 찾는 방법이다. 본 연구에서는 POD 기저벡터를 이용한 공력축소모델을 구축하고, 이를 전투기 날개문제에 적용하여 구하여진 정상상태 해와 Euler 해석 결과를 비교해 보았다. 또한 진동하는 익형문제에 적용하여 봄으로써 공탄성 해석에 적용 가능성 여부를 확인하였다.

• Annual Conference on Human and Language Technology
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• 2003.10d
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• pp.300-305
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• 2003

현재 우리나라의 표준 자판은 두벌식이며, 한글 입력기에 대한 연구도 두벌식을 중심으로 되어 왔다. 물론 세벌식도 있지만 널리 보급되지 못한 상태이며, 연구를 한다고 해도 글쇠배열 쪽으로 편향해 있지, 세벌식 구조자체에 대한 평가와 연구가 제대로 이루어지지 못한 실정이다. 본 연구에서는 <날개셋> 한글 입력기라는 새로운 입력기를 개발하여, 세벌식 글쇠배열을 응용한 효율적인 한글 입력 방식을 제안한다. 기존 연구들이 한국어와 한글 맞춤법의 특성을 살린 것이거나 세벌식과 두벌식을 절충하는 것이라면, 본 연구는 세벌식 자체의 장점을 살려 입력기의 내부 기능을 향상시켰다. 그래서 세벌식의 당위성을 단순한 글쇠 배열 차원의 능률이 아닌, 구조적이고 원천적인 관점에서 역설했다. 이들 고급 기능들은 초/중/종성을 순서 없이 쳐도 조합이 성립될 수 있는 세벌식 모아치기 원리에 근거를 두고 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.376-383
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• 1996

보(beam)는 기계 구조 및 항공 우주 구조물의 기본적인 요소로서, 특히 큰 동적 거동을 하는 경우는 비선형성이 두드러지게 나타나는 것으로 알려져 있고[4], 헬리콥터의 회전날개(rotor blade)나 두께가 얇은 고속회전 축등의 경우에는 비틀림(torsion)과 굽힘(bending) 운동이 비선형 연성되어 나타나게 된다. 이러한 비선형 연성 효과를 갖는 경우에는 운동의 양상이 복잡하게 전개된다. 따라서 본 연구에서는 비선형 연성운동이 생기는 이러한 단순 외팔보에 대해 비선형 진동 특성을 파악하고 각 비틀림(internal resonance)현상[5]에 따른 정상상태 진폭 응답의 해석을 그 목적으로 한다.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.1
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• pp.27-32
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• 2010

In this study, transonic flutter response characteristics have been studied for the AGARD 445.6 wing considering various turbulent models and several angle of attacks. The developed fluid-structure coupled analysis system is applied for flutter computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. The flutter boundaries of AGARD 445.6 wing are verified using developed computational system. For the nonlinear unsteady aerodynamics in high transonic flow region, DES turbulent model using the structured grid system have been applied for the wing model. Characteristics of flutter responses have been investigated for various angle of attack conditions. Also, it is typically shown that the current computation approach can yield realistic and practical results for aircraft design and test engineers.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.27-34
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• 2004

Tail-wing, gondola and thrust motor mount(EMS) were built by carbon/glass fiber composites. Structural strength & stiffness was verified by specimen tests. Static strength tests for each structural components were conducted separately. Boundary conditions are specially designed for each components to simulate exact joint conditions. Tests shows no detriment deformation at 100% DLL and no failure at 150% DLL.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.2
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• pp.17-26
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• 2006

The flutter characteristics of all movable tail wing with honeycomb sandwich structure have been studied in this study. The present wing model has a airfoil cross section and the linear variation of spanwise thickness. Structural vibration analysis is performed based on the finite element method using sandwich and beam elements. Unsteady aerodynamic technique used on the doublet lattice method has been effectively used to conduct the frequency-domain flutter analyses. The parametric flutter studies have been performed for various structural design parameters. Computational results on flutter stability due to the variation of structural parameters are presented and its related characteristics are investigated through the comparison of results.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.5
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• pp.343-348
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• 2013

When a natural frequency of the trailing edge of a wing is close to a vortex shedding frequency, an amplitude of the edge oscillation becomes maximal; it makes intensive noise called singing. Motion of the trailing edge may also feedback to the vortex shedding so that self-sustained oscillation appears, and a resonant frequency is locked in some interval of the speed of the incident flow. In this study, we first evaluate main features of oscillating characteristics of the wing. Second we simulate fluid-structure interaction of the wing with a flap using a commercial code, ANSYS-CFX, and investigate lift characteristics in a frequency domain.