• 천문학회보
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• 제46권1호
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• pp.29.1-29.1
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• 2021

There have been many studies aiming to reveal the origins of the star-gas misalignment found in galaxies, but there still is a lack of understanding of the contribution from each formation channel candidate. We explore the properties, origins, and lifetimes of the star-gas misalignment using Horizon-AGN, a large-volume cosmological simulation. First, the misalignment fraction shows a strong anti-correlation with the kinematic morphology (V/sigma) and the cold gas fraction of the galaxy. This result is consistent with the result of integral field spectroscopy observations. Second, we have identified four main formation channels of misalignment and quantified their level of contribution: mergers (35%), interaction with nearby galaxies (23%), interaction with dense environments or their central galaxies (21%), and secular evolution including smooth accretion from neighboring filaments (21%). Third, the decay timescale of the misalignment is strongly linked with the kinematic morphology of the galaxy: early-type galaxies (2.28 Gyr) tend to have a longer misalignment lifetime than LTGs (0.49 Gyr). We also found that the morphology and cold gas fraction are both and independently anti-correlated with the misalignment lifetime.

• 한국환경농학회지
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• 제29권1호
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• pp.20-26
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• 2010

제주도의 서북부 해안지역의 용암류 대지에 주로 분포하고 있으며 Ineeptisols로 분류되고 있는 동귀통을 재분류하고, 그 생성을 구명하기 위하여 동귀통 대표단면의 형태적 특성을 조사하고, Soil Taxonomy의 표준 분석방법인 Soilsurvey laboratorγ methods manual에 따라서토양을 분석하여 Laboratory data sheets를 작성하였다. Ap층(0~17 cm)은 농앙회갈색( 10YR 3/2)의 미사질양토이고, BA층(17~42 cm)은 농암회갈색(10YR 3/2)의 자갈이 있는 미사질양토, Bt1층(42~60 cm)은 농암회감색(10YR 3/2)의 자갈이 있는 미사절식양토, Bt2층(60~85 cm)은 암갈색(10YR 4/6)의 자갈이 있는 미사질식양토, BCt층(85~130cm)은 적갈색(5YR 4/3), 갈색(7.5YR 4/4), 또는 암회색(10YR 4/1)의 미사질식양토이다. 현무암 및 현무암에서 유래된 화산분출쇄설물을 모재로 하는 토양으로 주로 밭으로 이용되고 있다. udic 토양수분상과 thermie 토양온도상을 보유하며, 배수등급은 약간 양호이다. 동귀통은 andie 토양 특성을 보유하고 있지 않으며, 42~130cm 깊이에 점토집적층인 argillie층을 보유하고 있고, 전 토층에서 염기포화도(양이온 합)가 35% 이상으로 높다. 따라서 동귀통은 Ineeptisols이나 Andisols이 아니라 Alfisols로 분류되어야 한다. Udic 토양수분상을 보유하고 있으므로 동귀통은 Udalfs 아목으로 분류할 수 있으며, Hapludalfs의 분류조건을 충족시키고 있다. 또한 Typic 아군의 분류조건을 충족시키므로 Typic Hapludalfs로 분류할 수 있다. 토성속 제어부위에서의 토성속이 식양질이고, 토양온도상이 mesic 온도상이기 때문에 동귀통은 Fine silty, mixed, thermie famuily of Dystric Eutrudepts가 아니라 Fine loamy, mixed, thermic family of Typic Hapludalfs로 분류되어야 한다. 비교적 건조한 제주도 서부 및 북부 해안지방의 용압류대지에 주로 분포하는 동귀통은 화산분출에 의하여 형성된 화산분출쇄설물을 모재로 하고 있는데도 Andisols이 아니라 Alfisols로 생성 발달되고 있다. Andisols로 생성 발달되지 않은 동귀통은 안정한 지형인 용암류 대지에 분포하고 있으므로 토양이 거의 침식되지 않고 충적물이 별로 퇴적되지 않기 때문에 오랫동안 토양수의 하향이동에 따른 점토 집적작용과 염기 용탈작용을 받게 된다. 그 결과 점토집적층인 argillic층이 생성되고, 기준 깊이에서 염기포화도(양이온 합)가 35% 이상인 Alfisols로 생성발달하고 있다.

• 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.

• 제어로봇시스템학회논문지
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• 제17권12호
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• pp.1183-1187
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• 2011

In this paper, an optimal FIR (Finite-Impulse-Response) filter is proposed for discrete time-varying state-space models. The proposed filter estimates the current state using measured output samples on the recent time horizon so that the variance of the estimation error is minimized. It is designed to be linear, unbiased, with an FIR structure, and is independent of any state information. Due to its FIR structure, the proposed filter is believed to be robust for modeling uncertainty or numerical errors than other IIR filters, such as the Kalman filter. For a general system with system and measurement noise, the proposed filter is derived without any artificial assumptions such as the nonsingular assumption of the system matrix A and any infinite covariance of the initial state. A numerical example show that the proposed FIR filter has better performance than the Kalman filter based on the IIR (Infinite- Impulse-Response) structure when modeling uncertainties exist.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 B
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• pp.441-445
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• 1997

In this paper, we suggest a design scheme of receding horizon predictive control(RHPC) for boiler-turbine systems whose dynamics are given in nonlinear equations. RHPC is designed for linear state space models which are obtained at a nominal operating point of the boiler-turbine system. In this consideration, the boiler is operated in a sliding pressure mode, in which the reference value of drum pressure is changing according to the electrical power generation. The reference values of the system outputs are prefiltered before they are fed to the RHPC in order to compensate the linearization errors. Simulation results show that the proposed controller provides acceptable performances in both of the cases of 'steep and small changes' and 'slow and large changes' of power demand and yields the effect of modest coordination of conventional PID schemes such as boiler-following and turbine-following control.

• 한국광물학회지
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• 제10권1호
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• pp.45-49
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• 1997

Acid sulfate soils occur in the Gimhae plain where they have been formed from brackish alluvial sediments along the sea coast and river estuary. Acid sulfate soils suffer extremely acidity as a result of oxidation of pyrite. Total sulfur content of the soils was the highest in B horizon of Gimhae series and the lowest in A horizon of Deunggu series. The dominant fractions of sulfur in the soils were jarosite-S for Gimhae series, pyrite-S for Bongrim and Haecheog series, and organic-S for Deunggu series. The essential chemical processes of acid sulfate soils are, firstly, the formation of pyrite in waterlogged environment, and subsequently, the oxidation of this pyrite following natural or artificial drainage. Jarosite [K Fe3(SO4)2(OH)6] is a common sulfur mineral of the oxidation condition. Jarosite shows cubic particles with tetrahedral faces.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.83-83
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• 2001

• 천문학회지
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• 제48권4호
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• pp.213-228
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• 2015

The Horizon Run 4 is a cosmological N-body simulation designed for the study of coupled evolution between galaxies and large-scale structures of the Universe, and for the test of galaxy formation models. Using 6300³ gravitating particles in a cubic box of L_box = 3150 h⁻¹Mpc, we build a dense forest of halo merger trees to trace the halo merger history with a halo mass resolution scale down to M_s = 2.7 × 10¹¹h⁻¹M_⊙. We build a set of particle and halo data, which can serve as testbeds for comparison of cosmological models and gravitational theories with observations. We find that the FoF halo mass function shows a substantial deviation from the universal form with tangible redshift evolution of amplitude and shape. At higher redshifts, the amplitude of the mass function is lower, and the functional form is shifted toward larger values of ln(1/σ). We also find that the baryonic acoustic oscillation feature in the two-point correlation function of mock galaxies becomes broader with a peak position moving to smaller scales and the peak amplitude decreasing for increasing directional cosine μ compared to the linear predictions. From the halo merger trees built from halo data at 75 redshifts, we measure the half-mass epoch of halos and find that less massive halos tend to reach half of their current mass at higher redshifts. Simulation outputs including snapshot data, past lightcone space data, and halo merger data are available at http://sdss.kias.re.kr/astro/Horizon-Run4.

• 디지털융복합연구
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• 제20권4호
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• pp.617-625
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• 2022

본 연구는 기능에 따른 메타버스 플랫폼을 비교하고 분석하고자 하였다. 전문가 심층면접을 통해 5가지 메타버스 플랫폼을 선정하고 비교 분석하였다. 연구결과, 첫째 로블록스는 나만의 아바타를 커스터마이징하여 생성이 가능하며, 스튜디오 기능을 무료로 제공하며, 친구들과 프라이빗 게임을 즐길 수 있다. 둘째, 제페토는 셀카 한 장으로 아바타 생성이 가능하며, 크리에이티브 스튜디오 기능을 제공한다. 셋째, 포트나이트는 게임내 케릭터 생성이 가능하며, 게임에서 제공하는 아이템 구매 및 의복에 장치부착이 가능하고, 포크리 모드에서 친구들과 게임이 가능하다. 넷째, 게더타운은 가상공간의 유저들과 네트워킹이 가능하며, 나만의 아바타 커스터마이징 및 원하는 가상공간 템플릿이 제공된다. 끝으로, 페이스북 호라이즌은 직접 꾸민 자신만의 아바타로 가상세계 호라이즌에 참가하며, 월드 빌더라는 기능이 가능하고, 가상현실 속 광고판을 세우거나 가상의 매장이 가능하다. 본 연구는 메타버스 플랫폼의 특징을 통해 향후 산업에 적용할 수 있는 이론적 근거를 제공했다는 점에서 그 가치가 인정된다.

• 재무관리연구
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• 제24권2호
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• pp.183-206
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• 2007

The price-dividend ratio is one of the most frequently used financial variables to predict long-horizon stock return. However, the persistency of the price-dividend ratio is found to cause the spuriousness of the stock return prediction regression. The stable relationship between the stock price and the dividend, however, seems to weaken after World War II and to experience structural break. In this paper, we identify a structural change in the cointegrating relationship between the log of the stock price and the log of the dividend. Confirming a structural break in 1962, we subdivide the sample and apply the fully modified estimator to correct for the nonstationarity of the regressor. With the subdivided sample, we exercise the nonparametric bootstrap procedure to derive the empirical distribution of the test statistics and fail to find return predictability in each subsample period.