• 한국산학기술학회논문지
• /
• 제20권5호
• /
• pp.627-635
• /
• 2019

코딩 교육용 드론은 비행의 기초 원리를 체험하는 것뿐 아니라, 주로 아두이노(Arduino) 기반의 프로그래밍을 통해 드론을 제어하고 조종할 수 있도록 개발된 드론이다. 교육용 드론의 특성상 주 사용자는 드론 조종에 미숙한 학생들이기 때문에 드론과 외부 물체와의 충돌이 빈번하게 발생하여 드론 기체의 손상 비율이 높은 문제점이 있다. 본 연구에서는 교육용 드론 기체에 대한 구조 동역학 기반의 충돌 시뮬레이션 방법을 통해 드론의 구조적 안정성을 평가하였다. 약 240,000개의 4면체 요소를 갖는 해석 모델을 사용하여 $0^{\circ}$, $+15^{\circ}$, $-15^{\circ}$의 충돌 각도에 따른 3가지 케이스에 대해 충돌 시뮬레이션을 수행하였다. 3차원 구조물의 동적 거동 시뮬레이션에 탁월한 기능을 제공하는 ANSYS LS-DYNA를 활용하여 드론이 4 m/s의 속도로 벽에 충돌했을 때 주요 관심 부분인 드론 상 하부, 링 조립체에 발생하는 응력 분포 및 변형률을 분석하였다. 주요 관심 부분의 등가 응력에 따른 안전율은 0.72~2.64, 항복 변형률 기준 안전율은 1.72~26.67의 범위로 도출되었다. 이러한 안전율을 기준으로 재료 물성에 따른 항복 변형률과 종국 변형률을 초과하는 응력이 발생하는 부분에 대한 구조 안정성 확보를 위해 설계 보강이 필요한 부분을 제시한다.

• Journal of Astronomy and Space Sciences
• /
• 제34권3호
• /
• pp.213-223
• /
• 2017

The deep space orbit determination software (DSODS) is a part of a flight dynamic subsystem (FDS) for the Korean Pathfinder Lunar Orbiter (KPLO), a lunar exploration mission expected to launch after 2018. The DSODS consists of several sub modules, of which the orbit determination (OD) module employs a weighted least squares algorithm for estimating the parameters related to the motion and the tracking system of the spacecraft, and subroutines for performance improvement and detailed analysis of the orbit solution. In this research, DSODS is demonstrated and validated at lunar orbit at an altitude of 100 km using actual Lunar Prospector tracking data. A set of a priori states are generated, and the robustness of DSODS to the a priori error is confirmed by the NASA planetary data system (PDS) orbit solutions. Furthermore, the accuracy of the orbit solutions is determined by solution comparison and overlap analysis as about tens of meters. Through these analyses, the ability of the DSODS to provide proper orbit solutions for the KPLO are proved.

• 대한기계학회논문집A
• /
• 제26권8호
• /
• pp.1653-1665
• /
• 2002

One of the most significant problems in the processing of composite materials is residual stresses. The residual stresses may be high enough to cause cracking in the matrix even before external loads are applied and can degrade the integrity of composite structures. In this study, thermo-viscoelastic residual stresses occurred in the polymeric composite cylinder are investigated. This type of structure is used for the launch vehicle fuselage. The time and degree of cure dependent thermo-viscoelastic constitutive equations are developed and coupled with a thermo-chemical process model. These equations are solved with the finite element method to predict the residual stresses in the composite structures during cure. A launch vehicle experiences high thermal loads during flight and re-entry due to aerodynamic heating or propulsion heat, and the thermal loads may cause thermal buckling on the structure. In this study the thermal buckling analysis of composite cylinders are performed. Two boundary conditions such as all clamped and all simply supported are used for the analysis. The effects of laminates stacking sequences, shapes and residual stresses on the critical buckling temperatures of composite cylinders are investigated. The thermal buckling analysis is performed using ABAQUS.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회
• /
• pp.979-990
• /
• 2010

Although a centrifuge model test is performed with scaled models, it has a lot of advantages compared with usual scale model tests, for the reproduction of stress levels equal to a full scale test is possible. At the beginning of the Daewoo Institute of Construction Technology, a servo-motor-driven single axis actuator was introduced and has been in use with a geo-centrifuge. However, for variety of experiments and construction stage simulation, various apparatuses have been developed, such as a vacuum generator, a lateral actuator for tidal power simulation, a gravel hopper and a sand drainer for filled-up ground, and a water level controller. The apparatuses have been manufactured with enough strength and durability to be operated under specific g levels. This paper presents the properties of the apparatuses and the results of the tests performed with those.

• 한국항공운항학회지
• /
• 제25권3호
• /
• pp.35-43
• /
• 2017

Research for solar-powered high altitude long endurance(HALE) UAV was conducted by Korea Aerospace Research Institute(KARI), and the EAV-3 with 19.5m wing span was developed. For HALE flight, aircraft should be lightly designed. Especially, airframe structure that accounts for a large portion of the total weight of aircraft should be lightweight. In this paper, development process of airframe structure for solar-powered HALE UAV, EAV-3, is described briefly. Domestic developed T-800 grade CFRP(Carbon Fiber Reinforced Plastic) composite material with high modulus and strength was used to design main load carrying structures. Flightloads analysis that takes into account large structural deformation was carried out. Stress and flutter analyses for airframe structure sizing were conducted. Static strength test for main wing and aircraft ground vibration test were conducted successfully and structural integrity was secured.

• KSBB Journal
• /
• 제21권1호
• /
• pp.16-19
• /
• 2006

최근의 연구에 의하면 열이나, 산화적 스트레스에 대해서 NDPK는 구조적인 변화를 유발하며, 효소 활성과 구조가 oxidant에 의해 변화된다는 보고를 근거로 하여 정상적인 효모균주와 효모의 NDPK 유전자가 파괴된 mutant에서, 산화적 스트레스에 관련된 역할을 규명하고자 2-D 전기영동 방법을 통해서, $H_2O_2$의 처리전과 처리 후에 전사패턴이 변화된 유전자들, 즉, 산화적조절 신호체제에 연관되어졌을 것이라고 생각되어지는 몇 개의 단백질 리스트를 얻었다. 이 결과는 NDPK의 redox state의 조절에 관련된 효소의 성질을 규명함에 있어 유용한 유전자 신호 체제정보를 제공할 것으로 생각되어진다.

• Plant Biotechnology Reports
• /
• 제5권4호
• /
• pp.309-315
• /
• 2011

Rice grown in anaerobic waterlogged soil accumulates ammonium as a major source of nitrogen (N). We have compared the physiological symptoms of rice seedlings subjected to N-starvation stress with those receiving sufficient N, based on measurements of shoot/root length and weight and an analysis of protein expression patterns. N starvation marginally increased root growth but notably decreased shoot biomass. N uptake was reduced by >50% in the roots and shoots of N-starved seedlings. To better understand the mechanism of N starvation in rice, we performed a comparative proteome analysis of proteins isolated from rice leaves. Twenty-five differentially expressed proteins were analyzed by matrixassisted laser desorption/ionization time-of-flight (TOF) mass spectrometry and electron spray ionization quadrupole TOF. Functional analysis of the N-starvation response proteins suggested their involvement in protein synthesis and fate, metabolism, and defense. These results indicate that these proteins may play important roles in regulating the plant's complex adaptation responses for N use during N starvation. The proteins may be useful for further characterization of protein function in plant N nutrition.

• Advances in aircraft and spacecraft science
• /
• 제9권3호
• /
• pp.263-278
• /
• 2022

The time-varying structural reliability of an aeroelastic launch vehicle subjected to stochastic parameters is investigated. The launch vehicle structure is under the combined action of several stochastic loads that include aerodynamics, thrust as well as internal combustion pressure. The launch vehicle's main body structural flexibility is modeled via the normal mode shapes of a free-free Euler beam, where the aerodynamic loadings on the vehicle are due to force on each incremental section of the vehicle. The rigid and elastic coupled nonlinear equations of motion are derived following the Lagrangian approach that results in a complete aeroelastic simulation for the prediction of the instantaneous launch vehicle rigid-body motion as well as the body elastic deformations. Reliability analysis has been performed based on two distinct limit state functions, defined as the maximum launch vehicle tip elastic deformation and also the maximum allowable stress occurring along the launch vehicle total length. In this fashion, the time-dependent reliability problem can be converted into an equivalent time-invariant reliability problem. Subsequently, the first-order reliability method, as well as the Monte Carlo simulation schemes, are employed to determine and verify the aeroelastic launch vehicle dynamic failure probability for a given flight time.

• 항공우주시스템공학회지
• /
• 제18권4호
• /
• pp.27-33
• /
• 2024

본 연구는 드론에 다분광카메라와 열화상카메라를 장착하여 농작물의 건강 상태를 예측할 수 있는 식생지수(NDVI)를 획득하고 분석하는 정밀농업 기술을 실증하는 것에 대해 다룬다. 다분광카메라는 농작물의 반사율을 측정하여 식생지수를 계산하고, 열화상카메라는 작물의 온도 변화를 감지하여 수분 스트레스와 건강 상태를 평가한다. 이 연구를 통해 수집된 데이터는 농업 생산성을 높이고 화학 비료 및 농약 사용을 최적화할 수 있어 추후 사물 인식기술과 접목 하면 정밀농업 기술이 미래 농업의 지속 가능성을 향상하는 중요한 대안 기술로 자리 잡을 수 있음을 보여준다.

• 한국초지조사료학회지
• /
• 제25권4호
• /
• pp.287-296
• /
• 2005

프로테오믹스 기법을 이용하여 벼 저온 스트레스 관련 단백질을 분리 동정하기 위하여 저온 처리한 벼로부터 단백질을 분리하였다. 분리한 단백질로부터 Rubisco 단백질을 제거하기 위해 $15\%$ PEG fractionation을 실시한 후 $15\%$ PEG 상등액과 pellet 분획을 각각 이차원전기 영동으로 단백질을 분석하였고, MALDI-TOF MS를 이용하여 단백질을 동정하였다. $15\%$ PEG 상등액에서 8개의 단백질 spot이 증가하였고 10개의 spot 이 감소하였다. 증가한 8개 단백질 spot 중에서 epimerase/dehydratase, fructokinase, ribose-5-phosphate isomerase (Rpi), chaperonin 21 precursor, photosystem II oxygen-envolving complex (PS II OEC) protien 2 precursor, thioredoxin h-type (Trx-h) 등 6개의 단백질이 확인되어졌다. $15\%$ PEG pellet 분획에서 13개의 단백질 spot이 증가하였고 14 spot이 감소하였으며, 증가한 13개 단백질 spot중에서 OSJNB b059K02.15, hypothetical protein, mitogen-activated protein kinase kinase (MAPKK), 20S proteasome beta 7 subunit, Rubisco small subunit 등 5개의 단백질이 확인되어졌다. 확인되어진 단백질들은 기능별로 분류해 본 결과, 세포대사관련 단백질, energy 생성에 관련된 단백질, 산화환원 조절관련 단백질, 식물 병 방어관련, 단백질 합성 및 신호전달 관련 단백질 등으로 분류되었다. 이들 중 RPi와 MAPKK가 저온 스트레스에 의해 발현되는 것이 본 실험의 프로테옴 분석을 통하여 최초로 동정되었다.