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1984년 ~ 2025년까지 1,249 건의 한국우주과학회지를 계간으로 확인하실 수 있습니다.
- The Korean Space Science Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-052x (ISSN : 1225-052x)
1225-052x
- DB구축현황 : 1,249건 (DB Construction : 1,249 Articles)
총 게시글 1,249건
페이지 40/125
391
- Lee, Yong-Sam
- Journal of astronomy and space sciences
- 29, n.2
- pp.221-232
- 2012
- 원문 바로보기
We analyzed the manufacturing procedure, specifications, repair history, and details of celestial movements of the water-hammering type <TEX>$Honsang$</TEX> (celestial globe). Results from our study on the remaining <TEX>$Honsangs$</TEX> in China and Japan and on the reconstruction models in Korea were applied to our conceptual design of the water-hammering type <TEX>$Honsang$</TEX>. A <TEX>$Honui$</TEX> (armillary sphere) and <TEX>$Honsang$</TEX> using the water-hammering method were manufactured in <TEX>$Joseon$</TEX> in 1435 (the 17th year of King <TEX>$Sejong$</TEX>). <TEX>$Jang$</TEX> <TEX>$Yeong-Sil$</TEX> developed the <TEX>$Honsang$</TEX> system based on the water-operation method of <TEX>$Shui$</TEX> <TEX>$y{\ddot{u}}n$</TEX> <TEX>$i$</TEX> <TEX>$hsiang$</TEX> <TEX>$t'ai$</TEX> in China. Water-operation means driving water wheels using a water flow. The most important factor in this type of operation is the precision of the water clock and the control of the water wheel movement. The water-hammering type <TEX>$Honsang$</TEX> in <TEX>$Joseon$</TEX> probably adopted the <TEX>$Cheonhyeong$</TEX> (天衡; oriental escapement device) system of <TEX>$Shui$</TEX> <TEX>$y{\ddot{u}}n$</TEX> <TEX>$i$</TEX> <TEX>$hsiang$</TEX> <TEX>$t'ai$</TEX> in China and the overflow mechanism of <TEX>$Jagyeongnu$</TEX> (striking clepsydra) in <TEX>$Joseon$</TEX>, etc. In addition to the <TEX>$Cheonryun$</TEX> system, more gear instruments were needed to stage the rotation of the <TEX>$Honsang$</TEX> globe and the sun's movement. In this study, the water-hammering mechanism is analyzed in the structure of a water clock, a water wheel, the <TEX>$Cheonhyeong$</TEX> system, and the <TEX>$Giryun$</TEX> system, as an organically working operation mechanism. We expect that this study will serve as an essential basis for studies on <TEX>$Heumgyeonggaknu$</TEX>, the water-operating astronomical clock, and other astronomical clocks in the middle and latter parts of the <TEX>$Joseon$</TEX> dynasty.
392
- Kafka, Stella
- Journal of astronomy and space sciences
- 29, n.2
- pp.163-167
- 2012
- 원문 바로보기
Although the identification of the progenitors of type Ia supernovae (SNeIa) remains controversial, it is generally accepted that they originate from binary star systems in which at least one component is a carbon-oxygen white dwarf (WD); those systems are grouped under the wide umbrella of cataclysmic variables. Current theories for SNeIa progenitors hold that, either via Roche lobe overflow of the companion or via a wind, the WD accumulates hydrogen or helium rich material which is then burned to C and O onto the WD's surface. However, the specifics of this scenario are far from being understood or defined, allowing for a wealth of theories fighting for attention and a dearth of observations to support them. I discuss the latest attempts to identify and study those controversial SNeIa progenitors. I also introduce the most promising progenitor in hand and I present observational diagnostics that can reveal more members of the category.
393
- Sohn, Dong-Hyo
- Journal of astronomy and space sciences
- 29, n.1
- pp.1-10
- 2012
- 원문 바로보기
In this study, global positioning system (GPS)-derived precipitable water vapor (PWV) and microwave radiometer (MWR)-measured integrated water vapor (IWV) were compared and their characteristics were analyzed. Comparing those two quantities for two years from August 2009, we found that GPS PWV estimates were larger than MWR IWV. The average difference over the entire test period was 1.1 mm and the standard deviation was 1.2 mm. When the discrepancies between GPS PWV and MWR IWV were analyzed depending on season, the average difference was 0.7 mm and 1.9 mm in the winter and summer months, respectively. Thus, the average difference was about 2.5 times larger in summer than that in winter. However, MWR IWV measurements in the winter months were over-estimated than those in the summer months as the water vapor content got larger. The results of the diurnal analysis showed that MWR IWV was underestimated in the daytime, showing a difference of 0.8 mm. In the early morning hours, MWR IWV has a tendency to be over-estimated, with a difference of 1.3 mm with respect to GPS PWV.
394
- Sanborn, Jason J.
- Journal of astronomy and space sciences
- 29, n.1
- pp.63-67
- 2012
- 원문 바로보기
Observations with milliarsecond resolution using the Navy Optical Interferometer have been obtained for a number of stellar systems which include high-mass binaries, eclipsing binaries, and radio stars. These observations also reveal the previously unseen companions in single-lined spectroscopic binaries via directly measured flux ratios. We will present examples of published and ongoing research efforts of these systems to illustrate how an optical interferometer contributes to our knowledge of stars, their environment, and companions. These studies include a conclusive revealing of the previously unseen companion in the single-lined binary <TEX>${\Phi}$</TEX> Herculis, the direct determination of orbital parameters in the wide and close orbits of Algol, and revealing the orbit of <TEX>${\beta}$</TEX> Lyrae with spatially resolved images of the <TEX>$H{\alpha}$</TEX> emission.
395
- Kim, Eojin
- Journal of astronomy and space sciences
- 29, n.4
- pp.337-342
- 2012
- 원문 바로보기
In this study, the transient second or third layer on the topside of the Martian ionosphere were investigated with the most recently released Mars advanced radar for subsurface and ionospheric sounding/Mars Express data obtained from January 2010 to September 2011 to study the correlation between these topside additional layers and surface magnetic fields, solar zenith angle and solar activities. When examining the zones where the topside layer appeared, the occurrence rate of the topside layer was low at the areas with a strong Martian crustal magnetic field as observed by the Mars global surveyor. The occurrence rate of additional layers on the Martian topside ionosphere decreases as the solar zenith angle increases. However, these layers appeared significantly near the terminator of which solar zenith angle is <TEX>$90^{\circ}$</TEX>. In comparison between F10.7 which is the index of solar activities and the occurrence rate of the topside layer by date, its occurrence rate was higher in 2011 than in 2010 with less solar activities. The result of this study will contribute to better understanding of the environments in the topside of the ionosphere through the correlation between the various conditions regarding the Martian ionosphere and the transient layer.
396
Preliminary Test of Adaptive Neuro-Fuzzy Inference System Controller for Spacecraft Attitude Control
- Kim, Sung-Woo
- Journal of astronomy and space sciences
- 29, n.4
- pp.389-395
- 2012
- 원문 바로보기
The problem of spacecraft attitude control is solved using an adaptive neuro-fuzzy inference system (ANFIS). An ANFIS produces a control signal for one of the three axes of a spacecraft's body frame, so in total three ANFISs are constructed for 3-axis attitude control. The fuzzy inference system of the ANFIS is initialized using a subtractive clustering method. The ANFIS is trained by a hybrid learning algorithm using the data obtained from attitude control simulations using state-dependent Riccati equation controller. The training data set for each axis is composed of state errors for 3 axes (roll, pitch, and yaw) and a control signal for one of the 3 axes. The stability region of the ANFIS controller is estimated numerically based on Lyapunov stability theory using a numerical method to calculate Jacobian matrix. To measure the performance of the ANFIS controller, root mean square error and correlation factor are used as performance indicators. The performance is tested on two ANFIS controllers trained in different conditions. The test results show that the performance indicators are proper in the sense that the ANFIS controller with the larger stability region provides better performance according to the performance indicators.
397
- Yoon, Joh-Na
- Journal of astronomy and space sciences
- 29, n.4
- pp.397-405
- 2012
- 원문 바로보기
Astronomical Observations at Chungbuk National University Observatory (CBNUO) with an 1 m telescope have begun since April 2008, and Near-Earth Space Survey observations also have been started since November 2010, with a 0.6 m wide field telescope developed by Korea Astronomy and Space Science Institute. To improve observational efficiency, we developed a weather monitoring system enabling automatic monitoring for the weather conditions and checking the status of the observational circumstances, such as dome status. We hope this weather monitoring system can be helpful to more than 100 Korean domestic observatories, including public outreach facilities. In this paper, we present the statistic analysis of the weather conditions collected at CBNUO for 3 years (2009- 2011) and comparisons were made for clear nights between using only humidity data and both humidity and cloud data.
398
- Yim, Hyeon-Jeong
- Journal of astronomy and space sciences
- 29, n.3
- pp.287-293
- 2012
- 원문 바로보기
Satellite operating agencies are constantly monitoring conjunctions between satellites and space objects. Two line element (TLE) data, published by the Joint Space Operations Center of the United States Strategic Command, are available as raw data for a preliminary analysis of initial conjunction with a space object without any orbital information. However, there exist several sorts of uncertainties in the TLE data. In this paper, we suggest and analyze a method for estimating the uncertainties in the TLE data through mean, standard deviation of state vector residuals and covariance matrix. Also the estimation results are compared with actual results of orbit determination to validate the estimation method. Characteristics of the state vector residuals depending on the orbital elements are examined by applying the analysis to several satellites in various orbits. Main source of difference between the covariance matrices are also analyzed by comparing the matrices. Particularly, for the Korea Multi-Purpose Satellite-2, we examine the characteristics of the residual variation of state vector and covariance matrix depending on the orbital elements. It is confirmed that a realistic consideration on the space situation of space objects is possible using information from the analysis of mean, standard deviation of the state vector residuals of TLE and covariance matrix.
399
- Moon, Kyung Rok
- Journal of astronomy and space sciences
- 29, n.4
- pp.363-374
- 2012
- 원문 바로보기
This paper studies the problem of tracking a re-entry vehicle (RV) in order to predict its impact point on the ground. Re-entry target dynamics combined with super-high speed has a complex non-linearity due to ballistic coefficient variations. However, it is difficult to construct a database for the ballistic coefficient of a unknown vehicle for a wide range of variations, thus the reliability of target tracking performance cannot be guaranteed if accurate ballistic coefficient estimation is not achieved. Various techniques for ballistic coefficient estimation have been previously proposed, but limitations exist for the estimation of non-linear parts accurately without obtaining prior information. In this paper we propose the ballistic coefficient <TEX>${\beta}$</TEX> model-based interacting multiple model-extended Kalman filter (<TEX>${\beta}$</TEX>-IMM-EKF) for precise tracking of an RV. To evaluate the performance, other ballistic coefficient model based filters, which are gamma augmented filter, gamma bootstrapped filter were compared and assessed with the proposed <TEX>${\beta}$</TEX>-IMM-EKF for precise tracking of an RV.
400
- Oswalt, Terry D.
- Journal of astronomy and space sciences
- 29, n.2
- pp.175-180
- 2012
- 원문 바로보기
White dwarf stars have played important roles in rather diverse areas of astrophysics. This paper outlines how these stellar remnants, especially those in widely separated 'fragile' binaries, have provided unique leverage on difficult astrophysical problems such as the ages of stars, the structure and evolution of the Galaxy, the nature of dark matter and even the discovery of dark energy.