• Journal of Astronomy and Space Sciences
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• 제21권3호
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• pp.209-220
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• 2004

Some methods have been presented to get optimal formation trajectories in the step of configuration or reconfiguration, which subject to constraints of collision avoidance and final configuration. In this study, a method for optimal formation trajectory-planning is introduced in view of fuel/time minimization using parameter optimization technique which has not been applied to optimal trajectory-planning for satellite formation flying. New constraints of nonlinear equality are derived for final configuration and constraints of nonlinear inequality are used for collision avoidance. The final configuration constraints are that three or more satellites should be placed in an equilateral polygon of the circular horizontal plane orbit. Several examples are given to get optimal trajectories based on the parameter optimization problem which subjects to constraints of collision avoidance and final configuration. They show that the introduced method for trajectory-planning is well suited to trajectory design problems of formation flying missions.

• International Journal of Aeronautical and Space Sciences
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• 제12권1호
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• pp.16-23
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• 2011

In this paper, nonlinear model predictive control (NMPC) is addressed to develop formation guidance for multiple unmanned aerial vehicles. An NMPC algorithm predicts the behavior of a system over a receding time horizon, and the NMPC generates the optimal control commands for the horizon. The first input command is, then, applied to the system and this procedure repeats at each time step. The input constraint and state constraint for formation flight and inter-collision avoidance are considered in the proposed NMPC framework. The performance of NMPC for formation guidance critically degrades when there exists a communication failure. In order to address this problem, the modified optimal guidance law using only line-of-sight, relative distance, and own motion information is presented. If this information can be measured or estimated, the proposed formation guidance is sustainable with the communication failure. The performance of this approach is validated by numerical simulations.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.34.3-34.3
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• 2009

We have investigated the recent star formation history of the nearby galaxies using the SDSS optical and Galex UV data. To everyone's surprise, we found that roughly 30 percent of elliptical galaxies had a residual star formation in the last billion years, suggesting that residual star formation has been common even in ellipticals. Galaxy evolution models based on semi-analytic prescriptions including AGN feedback reasonably reproduce the star formation properties of elliptical galaxies. However, we found that the current galaxy models miserably fail to reproduce the star formation properties of satellite disc galaxies in cluster environments. Satellite disc galaxies in models are overly star-formation quenched in comparison to observation. Detailed investigations led us to conclude that this is due to the use of inaccurate prescriptions for the gas content evolution in the model. I present a solution to the problem by adopting more realistic physical prescriptions.

• 천문학회보
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• 제38권1호
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• pp.65.2-65.2
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• 2013

A presence of a penumbra is one of the main properties of a mature sunspot, and its formation mechanism has been elusive due to a lack of observations that fully cover the formation process. Utilizing the New Solar Telescope at the Big Bear Solar Observatory, we observed the formation of a partial penumbra for about 7 hours simultaneously at the photospheric (TiO; $7057{\AA}$) and the chromospheric ($H{\alpha}$, $-1{\AA}$) spectral lines with high spatial and temporal resolution. From this uninterrupted, long observational sequence, we found that flux emergence under the stable chromospheric canopy fields resulted in penumbra formation, while emerging flux under the expanding chromospheric fields appeared as transient elongated granules. Based on these findings, we suggest a possible scenario for penumbra formation in which a penumbra forms when the emerging flux is constrained from continuing to emerge, but rather is trapped at the photospheric level by the overlying chromospheric canopy fields.

• International Journal of Aeronautical and Space Sciences
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• 제10권1호
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• pp.30-36
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• 2009

Many formation guidance laws have been proposed for VAV formation flight. Since most autonomous formation flight methods require various active communication links between the vehicles to know motion information of other vehicles, damage to the receiver or the transmitter and communication delay are critical problem to achieve a given formation flight mission. Therefore, in this point of view, the method that does not need an inter-vehicle communication is preferred in the autonomous formation flight. In this paper, we first summarize the formation guidance law without an inter-vehicle communication using feedback linearization and sliding mode control proposed in previous study. We also propose the modified formation guidance law with robust disturbance observer, which can provide significantly better performance than previously mentioned guidance law in case that other vehicles maneuver with large accelerations. The robust disturbance observer can estimate uncertainties generated by acceleration of leader vehicle. By eliminating the uncertainties using the estimated uncertainties, VAVs are able to achieve the tight formation flight. The performance of the proposed approach is validated by numerical simulations.

• 한국게임학회 논문지
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• 제21권3호
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• pp.25-38
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• 2021

본 논문은 현대인의 생활에서 많은 비중을 차지하게 된 디지털 게임 공간에 대해 시뮬라크르 이론에 따라 인간 실존적 의미의 장소(place)로의 발전 가능성과 장소성(placeness) 형성 과정에 대해 알아본다. 우선 인간과 관계 맺음 하는 디지털 게임 공간을 플라톤, 장 보드리야르, 질 들뢰즈의 시뮬라크르 이론을 바탕으로, 혼재될 수 있는 세 가지의 시뮬라크르 공간 양상으로 해석했다. 게임 공간에서 장소성이 형성되는 과정을 앞서 재해석한 시뮬라크르 공간과 장소 이론, 그리고 사용자의 게임 경험을 연결 지어 제시하였다. 이를 통해 다양한 매체의 진정성 있는 경험을 위한 디지털 게임 공간의 장소 양상을 탐구하는 데 이바지하길 기대한다.

• 한국실내디자인학회논문집
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• 제14권3호
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• pp.156-164
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• 2005

Like other countries undergoing the aging of the population, increases in the aged population have raised serious issues in Korea. The proportion of elderly will be foreseen over $14\%$ of population in 2019, over $20\%$ in 2026 in korea. Due to the rapid increasing in the aged population, it calls for social countermeasures urgently, And recent researches about attitude to the aged find out in general negative attitude to the aged of other generations. It is thought desirable that comprehension to the aged of the commonalty should be educated on the school basis or a variety of informal ways. The study aims to determine the space formation of the senior simulation center that suggest to be considered for the effective education and preparation for the aging of all social members, particularly for the younger generation. In such space formation, it is important to work out a plan of efficiency education according to the systematic environmental setting with a focus on the minimization of problematic behaviors and living disabilities of aging, as interactive experiences gain malfunctions by aging. This study is expected to promote a focus on the integration of the whole generations and improved design management for the environment of a welfare policy for the aged.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2001년도 한국우주과학회보 제10권2호
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• pp.17-17
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• 2001

• 한국주거학회논문집
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• 제20권5호
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• pp.9-21
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• 2009

This study classified visual perception types of access space at 17 five-star hotels in Jejudo and examined their cognitive characteristics and image formation structures in an effort to provide basic information important for designing the elevation and the access spaces of a hotel. The results of this study are as follows. Access space image of experimental hotels showed more negative evaluations at both city hotels and resort hotels, viewing angle (upward angle) was also positively evaluated between $10^{\circ}{\sim}12^{\circ}$ and $18^{\circ}$ and central type in arrangement type and detour access and straight access types in access circulation type were positively evaluated. When viewed from an upward angle of $10^{\circ}$ to $12^{\circ}$, the most important factors were as plasticity, decorativeness, and creativity; from $18^{\circ}$ it was such factors as harmony and peculiarity; and at $45^{\circ}$ it was factors like decorativeness and stability. In considering the various access types, the most important factors in a straight access type were peculiarity and harmony; for one-time curved access type it was by decorativeness, creativity, Peculiarity, and stability; and for detour access types it was decorativeness, stability, and peculiarity. Influential of factors affecting image formation and plasticity and harmony factors and the form had more influences on image formation.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2007년도 한국우주과학회보 제16권1호
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• pp.49-49
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• 2007