• Advances in aircraft and spacecraft science
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• 제5권1호
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• pp.73-105
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• 2018

A particular type of constant speed helical trajectory, with variable ascension rate, is proposed. Such trajectories are candidates of choice as motion primitives in automatic airplane trajectory planning; they can also be used by airplanes taking off or landing in limited space. The equations of motion for airplanes flying on such trajectories are exactly solvable. Their solution is presented, together with an analysis of the restrictions imposed on the geometrical parameters of the helical paths by the dynamical abilities of an airplane. The physical quantities taken into account are the airplane load factor, its lift coefficient, and the thrust its engines can produce. Formulas are provided for determining all the parameters of trajectories that would be flyable by a particular airplane, the final altitude reached, and the duration of the trajectory. It is shown how to construct speed interval tables, which would appreciably reduce the calculations to be done on board the airplane. Trajectories are characterized by their angle of inclination, their radius, and the rate of change of their inclination. Sample calculations are shown for the Cessna 182, a Silver Fox like unmanned aerial vehicle, and the F-16 Fighting Falcon.

• Journal of Astronomy and Space Sciences
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• 제32권4호
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• pp.317-325
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• 2015

Energy spectra of electron microbursts from 170 keV to 340 keV have been measured by the solid-state detectors aboard the low-altitude (680 km) polar-orbiting Korean STSAT-1 (Science and Technology SATellite). These measurements have revealed two important characteristics unique to the microbursts: (1) They are produced by a fast-loss cone-filling process in which the interaction time for pitch-angle scattering is less than 50 ms and (2) The e-folding energy of the perpendicular component is larger than that of the parallel component, and the loss cone is not completely filled by electrons. To understand how wave-particle interactions could generate microbursts, we performed a test particle simulation and investigated how the waves scattered electron pitch angles within the timescale required for microburst precipitation. The application of rising-frequency whistler-mode waves to electrons of different energies moving in a dipole magnetic field showed that chorus magnetic wave fields, rather than electric fields, were the main cause of microburst events, which implied that microbursts could be produced by a quasi-adiabatic process. In addition, the simulation results showed that high-energy electrons could resonate with chorus waves at high magnetic latitudes where the loss cone was larger, which might explain the decreased e-folding energy of precipitated microbursts compared to that of trapped electrons.

• 천문학회지
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• 제34권1호
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• pp.25-29
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• 2001

We have constructed a non-spherical model for the hot oxygen corona of Mars by including the effects of planetary rotation and diurnal variation of the Martian ionosphere. Exospheric oxygen densities are calculated by integrating ensemble of ballistic and escaping oxygen atoms from the exobase over the entire planet. The hot oxygen atoms are produced by dissociative recombination of $O^+_2$, the major ion in the Martian ionosphere. The densities of hot oxygen atoms at the exobase are estimated from electron densities which have been measured to vary with solar zenith angle. Our model shows that the density difference of hot oxygen atoms between noon and terminator is about two orders of magnitude near the exobase, but reduces abruptly around altitudes of 2000 km due to lateral transport. The diurnal variation of hot oxygen densities remains significant up to the altitude of 10000 km. The diurnal variation of the hot oxygen corona should thus be considered when the upcoming Nozomi measurements are analyzed. The non-spherical model of the hot oxy-gen corona may contribute to building sophisticate solar wind interaction models and thus result in more accurate escaping rate of oxygens from Mars.

• 항공우주산업기술동향
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• 제7권2호
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• pp.115-120
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• 2009

본 논문에서는 원형마크를 이용한 항공기와 활주로간의 새로운 거리측정시스템에 관한 내용이다. 이 시스템은 항공기에 카메라와 고도계를 장착하고 활주로에 원형마크가 있어야 한다. 항공기에 장착된 카메라는 반드시 항공기의 진행방향을 향하면서 원형마크를 영상이미지형태로 간파하여 이미 장착한 고도계의 고도값과 함께 비행조종컴퓨터가 항공기와 지상간의 각도, 항공기와 원형마크간의 지상거리, 그리고 기울기거리를 계산하여야 한다. 이 시스템은 무인기의 자동착륙에 사용될 수 있다.

• International Journal of Aeronautical and Space Sciences
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• 제11권3호
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• pp.167-174
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• 2010

The design, dynamics, and control allocation of tri-rotor unmanned aerial vehicles (UAVs) are introduced in this paper. A trirotor UAV has three rotor axes that are equidistant from its center of gravity. Two designs of tri-rotor UAV are introduced in this paper. The single tri-rotor UAV has a servo-motor that is installed on one of the three rotors, which enables rapid control of its motion and its various attitude changes-unlike a quad-rotor UAV that depends only on the angular velocities of four rotors for control. The other design is called 'coaxial tri-rotor UAV,' which has two rotors installed on each rotor axis. Since the tri-rotor type of UAV has the yawing problem induced from an unpaired rotor's reaction torque, it is necessary to derive accurate dynamic and design control logic for both single and coaxial tri-rotors. For that reason, a control strategy is proposed for each type of tri-rotor, and nonlinear simulations of the altitude, Euler angle, and angular velocity responses are conducted by using a classical proportional-integral-derivative controller. Simulation results show that the proposed control strategies are appropriate for the control of single and coaxial tri-rotor UAVs.

• 조명전기설비학회논문지
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• 제17권6호
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• pp.7-15
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• 2003

본 연구는 RADIANCE 프로그램을 이용하여 블라인드가 설치된 창문의 투과율을 휘도계산을 통해 결정하고자 한다. 천공의 종류, 계절의 변화, 태양의 고도 및 방위각의 변화, 블라인드의 각도 0$^{\circ}$, 45$^{\circ}$, 90$^{\circ}$등을 매개변수로 고려하였고, 시뮬레이션에 의한 블라인드 투과율은 블라인드 방향성 등의 특성에 따라 다양한 결과로 나타났다. 이러한 결과를 조명계산과 광센서 조광제어시스템의 분석 도구로 사용될 수 있는 프로그램인 DayDim에 적용할 수 있는 방법론을 제시하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제39권2호
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• pp.152-158
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• 2015

Unlike photovoltaic systems installed on land, photovoltaic systems applied to the offshore plant have the characteristic that is installed in a limited space. For single point mooring plant, it is advantageous in terms of a reliable power supply to be installed in different directions of photovoltaic panels, because it is not possible to identify the position of the sun by rotation of the plant itself. Differences of installation angle between photovoltaic panels make a difference of the intensity of radiation irradiated on each photovoltaic panel, and it brings loss of generation quantity due to the partial shading. In order to provide a photovoltaic system suitable for offshore plant, the modeling which contains multiple photovoltaic panels controlled by single controller is performed. Then, it was examined how the output characteristics of the photovoltaic system change about the difference of the intensity of radiation that varies depending on the altitude of the sun. Finally, through the simulation, a development model of the photovoltaic system which is suitable for offshore plant is suggested.

• KIEAE Journal
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• 제3권2호
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• pp.45-50
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• 2003

Today, there are increasing evidences that daylight is essential for health, well-being and productivity. One of the strong contributions, which atria can make to advantages in building, is in allowing the use of daylight. This research is to develop nomographs and to evaluate the daylight performances of toplit atria with louvers. For this purpose, the evaluation models of toplit atria with well indexes of 0.5, 1.0 or 2.0 have been selected through the field surveys of atrium buildings in Seoul area. Also, weather data for solar irradiance and luminous efficacy were gathered from the recently conducted previous researches. The computer simulations were performed under clear sky conditions, using the ADELINE program, and various daylight performances were analyzed by the daylight illumination ratio. Analyzing the simulation results, solar altitude, solar azimuth, and louver angle and louver reflectance were found to be important factors affecting the daylight performance of toplit atria. Using these variables, regression equations have been formulated, and the nomographs, which may predict the daylight performances of toplit atria with louvers, were developed. The developed nomographs were validated through comparing the results of nomograph predictions to the results of scale-model experiments.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.303-308
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• 2006

HyShot 스크램제트 엔진의 연소 특성을 살펴보기 위해 수치해석을 수행하였다. 고도, 받음각, 당량비는 각각 28km, $0^{\circ}$, 0.426으로 주어졌다. $H_2$ 및 OH 질량 분율로부터 분사기 상류 재순환 영역의 화염지지기구 역할 및 주된 연소가 카울로부터 15cm 후방에서 시작됨을 알 수 있었다. 2차원 해석은 HyShot 스크램제트 엔진의 연소기 내부 압력을 비교적 잘 모사하고 있으며, 또한 주기적 연소 특성을 보여준다.

• 천문학회보
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• 제39권2호
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• pp.110.1-110.1
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• 2014

The optics of Space telescope is one of the major parts of space mission used for imaging observation of astronomical targets and the Earth. These kinds of space mission have a bulky and complex opto-mechanics with a long optical tube, but there are attempts have been made to observe a target with a small satellite in many ways. In this paper, we describe an optical design of a reflecting telescope for use in a CubeSat mission. For this design, we adopt the off-axis segmented method of astronomical observation techniques based on the Ritchey-Chr$\acute{e}$tien type telescope. The primary mirror shape is a rectangle with dimensions of $8cm{\times}8cm$, and a secondary mirror has dimensions of $2.4cm{\times}4.1cm$. The focal ratio is 3 which can obtain a $0.3{\times}0.2$ degree diagonal angle in a $1280{\times}800$ CMOS color image sensor with a pixel size of $3{\mu}m{\times}3{\mu}m$. This optical design can capture a ${\sim}4km{\times}{\sim}2.3km$ area of the earth's surface at 700 km altitude operation. Based on this conceptual design, we will keep trying to study more for astronomical observation with Attitude control system.