• 항공우주시스템공학회지
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• 제16권2호
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• pp.63-72
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• 2022

초소형위성에 대한 관심이 증가함에 따라 초소형위성군의 성능과 활용도뿐 아니라 위성군의 궤도설계, 궤도배치 기법에 대한 연구가 활발히 수행되고 있다. 본 연구에서는 초소형 위성을 활용한 워커-델타 위성군을 구축하기 위한 궤도배치 기법으로 추력을 이용한 기법과 차등 대기항력 제어 (DADC)를 연구하였다. 추력을 이용할 시, 발사체에 대한 위성의 분리속도와 각도에 따라 궤도배치에 소요되는 시간과 추력량이 달라진다. 초소형위성의 추력시스템 성능을 참고하여 제한된 성능으로 궤도배치를 완료하기 위한 제어전략을 제시하였다. 결과적으로 궤도배치 기간과 총 추력량의 관계를 도출하였다. 차등 대기항력을 이용하면 추력을 소모하지 않는 대신 상대적으로 긴 배치기간을 소요한다. 소프트웨어 시뮬레이션을 통해 일반적인 초소형위성군의 궤도에서 차등 대기항력으로 궤도배치를 완료할 수 있음을 검증하였다. 본 연구 결과를 활용하면 초소형위성군의 궤도배치에 전략을 수립하고 활용할 수 있을 것이다.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.123-130
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• 2005

In this study, we evaluated the CH4 and CO conversion efficiencies over the oxidation catalysts for natural gas vehicle with lean-burn system. On the fresh catalyst, the conversion efficiency was increased when the loading of precious metal was increased. On the aged catalyst, the conversion efficiency was decreased as increasing the excess air ratio. We could confirm the measuring conversion efficiency of the unsteady state with the FTIR and that of steady state with the GC The temperature increasing ratio of unsteady state is acceptable from 3$^{\circ}C$/min. to 15$^{\circ}C$/min. for the evaluation of catalyst conversion performance , which has within the 4$\%$ of the difference of conversion efficiency. We observed a physical behavior of the thermal aged catalyst's surface using TEM and BET device. It was found that the precious metal was grown to the micro-scopic size by thermal aging process.

• International Journal of Aeronautical and Space Sciences
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• 제12권1호
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• pp.84-91
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• 2011

A finite element analysis for the wing and landing gear of a composite target-drone air vehicle was performed. For the wing analysis, two load cases were considered: a 5g symmetric pull-up and a -1.5g symmetric push-over. For the landing gear analysis, a sinking velocity of 1.4 m/s at a 2g level landing condition was taken into account. MSC/NASTRAN and LS-DYNA were utilized for the static and dynamic analyses, respectively. Finite element results were verified by the static test of a prototype wing under a 6g symmetric pull-up condition. The test showed a 17% larger wing tip deflection than the finite element analysis. This difference is believed to come from the material and geometrical imperfections incurred during the manufacturing process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.231-234
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• 2001

OBD-II regulations are already effective in many countries. The California Air Resources Board(CARB) first issued regulations in 1985 for the 1988 model year, known as OBD-I, and required the vehicle's engine management computer to warn the driver by means of a dash-mounted light if a malfunction occurred in either the oxygen sensor, the exhaust gas recirculation(EGR) valve or the evaporative emission system purge solenoid, and to store information on troubles that have no recurrent characteristics. This paper presents two methods of wireless monitoring OBD signal, which is one of the ECU output for self diagnostic measurement. RF module is used to monitor ECU's Self diagnostic signal remotely. Two kinds of measurement systems which are based on micro-controller(80C196KC) for portable detection and PC for sever are considered for receiving the RF signal. Therefore, possibility of real-time monitoring of ECU's self diagnostic signal remotely is verified on this paper.

• Advances in aircraft and spacecraft science
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• 제2권3호
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• pp.303-328
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• 2015

A design methodology is presented to develop the hingeless control surfaces for MAV using adhesively bonded Macro Fiber Composite (MFC) actuators. These actuators have got the capability to deflect the trailing edge surfaces of the wing to attain the required maneuverability, besides achieving the set aerodynamic trim condition. A scheme involving design, analysis, fabrication and testing procedure has been adopted to realize the trailing edge morphing mechanism. The stiffness distribution of the composite MAV wing is tailored such that the induced deflection by piezoelectric actuation is approximately optimized. Through ground testing, the proposed concept has been demonstrated on a typical MAV structure. Electromechanical analysis is performed to evaluate the actuator performance and subsequently aeroelastic and 2D CFD analyses are carried out to see the functional requirements of wing trailing edge surfaces to behave as elevons. Efforts have been made to obtain the performance comparison of conventional control surfaces (elevons) with morphing wing trailing edge surfaces. A significant improvement in lift to drag ratio is noticed with morphed wing configuration in comparison to conventional wing. Further, it has been shown that the morphed wing trailing edge surfaces can be deployed as elevons for aerodynamic trim applications.

• 환경영향평가
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• 제16권4호
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• pp.241-250
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• 2007

A study was carried out on the level of heavy metals, total coliform and benzo(a)pyrene that may be introduced through by-product fertilizers or air pollution to turfgrass in natural turfgrass playground in elementary schools around the western coast and eastern mountain areas in Jeollabuk-do, Korea. The level of heavy metals found in turfgrass was in the order of Cu > Zn > Pb > Cd. The majority of heavy metals was found in the roots. It is presumed that the absorption of some air pollutants and by-product fertilizers or chemical fertilizers. The level of benzo(a)pyrene showed an average of 0.05ng/g with a range between 0.02 to 0.08ng/g in the leaves. In the meantime, none was detected in the stems, while the average for roots was 0.02ng/g with a range between 0.01 and 0.03ng/g. The level detected is that found background level, however, benzo(a)pyrene can be introduced partly from the unstable combustion of fossil fuel or through vehicle emissions. Total coliform distributed in grass showed an average of 12MPN/100ml with a range between 2 and 36MPN/100ml. The density of total coliform displayed no regional predominance. However, in some urban areas, the density was slightly higher. The feces of pets or by-product fertilizers may have contributed to the input of pathogenic micro-organism. Yet the level was found to be negligible.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.311-314
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• 2007

곤충의 날개짓을 모방한 공력특성 연구가 초소형 비행체의 설계 파라미터를 구하기 위하여 수행되었다. 한 쌍의 날개 모델은 초파리(rosophila) 날개짓을 모방하기 위하여 200배 확대하였으며, 두 쌍의 공간 4절 링크를 적용하였다. Weis-Fogh 메커니즘을 검증하기 위해 한 쌍의 날개모델은 후행회전(Delayed Rotation)의 움직임을 가지도록 설계되었다. 또한 양력 및 항력은 날개 끝 속도 기준 레이놀즈수 약 1200, 최대 받음각 $40^{\circ}$에서 측정되었다. 모델의 관성력은 99.98%의 진공 챔버로 측정되고 공기속에서 측정된 데이터에서 제거되었다. 본 연구에서 Weis-Fogh 메커니즘의 고양력 효과는 날개의 업스트로크 과정에서 나타났다.

• Environmental Analysis Health and Toxicology
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• 제28권
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• pp.7.1-7.9
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• 2013

Objectives We investigated the particle mass size distribution and chemical properties of air pollution particulate matter (PM) in the urban area and its capacity to induce cytotoxicity in human bronchial epithelial (BEAS-2B) cells. Methods To characterize the mass size distributions and chemical concentrations associated with urban PM, PM samples were collected by a 10-stage Micro-Orifice Uniform Deposit Impactor close to nearby traffic in an urban area from December 2007 to December 2009. PM samples for in vitro cytotoxicity testing were collected by a mini-volume air sampler with $PM_{10}$ and $PM_{2.5}$ inlets. Results The PM size distributions were bi-modal, peaking at 0.18 to 0.32 and 1.8 to $3.2{\mu}m$. The mass concentrations of the metals in fine particles (0.1 to $1.8{\mu}m$) accounted for 45.6 to 80.4% of the mass concentrations of metals in $PM_{10}$. The mass proportions of fine particles of the pollutants related to traffic emission, lead (80.4%), cadmium (69.0%), and chromium (63.8%) were higher than those of other metals. Iron was the dominant transition metal in the particles, accounting for 64.3% of the $PM_{10}$ mass in all the samples. We observed PM concentration-dependent cytotoxic effects on BEAS-2B cells. Conclusions We found that exposure to $PM_{2.5}$ and $PM_{10}$ from a nearby traffic area induced significant increases in protein expression of inflammatory cytokines (IL-6 and IL-8). The cell death rate and release of cytokines in response to the $PM_{2.5}$ treatment were higher than those with $PM_{10}$. The combined results support the hypothesis that ultrafine particles from vehicular sources can induce inflammatory responses related to environmental respiratory injury.

• 한국항공우주학회지
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• 제38권7호
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• pp.637-646
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• 2010

포텐셜 기저 패널법과 시간전진법을 통합한 시간영역 패널법을 이용하여 융합익기 형상 초소형 무인기 FM07에 대한 정상/비정상 공력해석을 수행하였다. 융합익기 형상 무인기인 FM07의 공력해석에는 초기 설계형상(Case I)과 가로세로비를 증가시키고 무게중심을 후방으로 이동시킨 개선형상(Case II)이 사용되었다. 정상 공력해석을 통해 FM07 무인기의 개선형상이 초기형상에 비하여 보다 큰 양항비와 높은 피칭 안정성을 나타냄을 확인하였다. FM07의 비정상 급가속(발사체 이륙단계)을 나타낸 공력해석에서는 초기 급격한 증가를 보이는 공력계수들이 수초 후에 안정화되어 정상상태에 근사한 값을 나타내었다. FM07의 순항시 발생할 수 있는 피치진동운동에 대한 해석을 수행하여 진동에 따른 공력계수의 이력 현상을 확인하였으며, 개선형상이 보다 큰 민감도를 갖는 것을 확인하였다.

• 한국항공우주학회지
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• 제34권1호
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• pp.56-64
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• 2006

본 논문에서는 전도성 형상기억폴리우레탄 (CSMPU)의 개발과 응용 방법이 연구되었다. 일반적인 형상기억폴리우레탄이 외부 열원에 의해 작동되어 온 반면에, 2004년에 소개된 전도성 형상기억폴리우레탄은 전력에 의해 작동되었다. 전도성 형상기억폴리우레탄 작동기는 일반적인 형상기억폴리우레탄에 카본 나노 튜브를 첨가함으로써 제작되었다. 2004년 연구에서 제작된 전도성 형상기억폴리우레탄이 지닌 핵심 문제점은 카본 나노 튜브의 낮은 분산도였다. 이 논문에서는 분산 문제 해결을 시도하였으며, 일련의 정교한 작업을 통해 향상된 전기적 특성을 지닌 전도성 형상기억폴리우레탄 작동기를 개발하였다. 그리고 개발된 전도성 형상기억폴리우레탄 작동기의 작동 성능을 측정 및 평가하였으며, 초소형비행체 조종면의 제어 실험을 통하여 응용 가능성을 검토하였다.