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1984년 ~ 2025년까지 1,255 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 : 1,255건 (DB Construction : 1,255 Articles)
총 게시글 1,255건
페이지 42/126
411
- Ryu, Kwang-Sun
- Journal of astronomy and space sciences
- 29, n.3
- pp.315-320
- 2012
- 원문 바로보기
We developed a mass-memory chip by staking 1 Gbit double data rate 2 (DDR2) synchronous dynamic random access memory (SDRAM) memory core up to 4 Gbit storage for future satellite missions which require large storage for data collected during the mission execution. To investigate the resistance of the chip to the space radiation environment, we have performed heavy-ion-driven single event experiments using Heavy Ion Medical Accelerator in Chiba medium energy beam line. The radiation characteristics are presented for the DDR2 SDRAM (K4T1G164QE) fabricated in 56 nm technology. The statistical analyses and comparisons of the characteristics of chips fabricated with previous technologies are presented. The cross-section values for various single event categories were derived up to ~80 <TEX>$MeVcm^2/mg$</TEX>. Our comparison of the DDR2 SDRAM, which was fabricated in 56 nm technology node, with previous technologies, implies that the increased degree of integration causes the memory chip to become vulnerable to single-event functional interrupt, but resistant to single-event latch-up.
412
- Oh, Sung-Jin
- Journal of astronomy and space sciences
- 29, n.2
- pp.103-113
- 2012
- 원문 바로보기
The ButterStar Observatory at the Dongducheon High School has been working for photographic observations of the Sun since October 16, 2002. In this study, we observed the Sun at the ButterStar observatory for 3,364 days from October 16, 2002 to December 31, 2011, and analyzed the photographic sunspot data obtained in 1,965 days. The correction factor <TEX>$K_b$</TEX> for the entire observing period is 0.9519, which is calculated using the linear least square method to the relationship between the daily sunspot number, <TEX>$R_B$</TEX>, and the daily international relative sunspot number, <TEX>$R_i$</TEX>. The yearly correction factor calculated for each year varies slightly from year to year and shows a trend to change along the solar cycle. The correction factor is larger during the solar maxima and smaller during the solar minima in general. This implies that the discrepancy between a relative sunspot number, R, and the daily international relative sunspot number, <TEX>$R_i$</TEX>, can be reduced by using a yearly correction factor. From 2002 to 2008 in solar cycle 23, 35.4% and 64.6% of sunspot groups and 35.1% and 64.9% of isolated sunspots in average occurred in the northern hemisphere and in the southern hemisphere, respectively, and from 2008 to 2011 in solar cycle 24, 61.3% and 38.7% of sunspot groups and 65.0% and 35.0% of isolated sunspots were observed, respectively. This result shows that the occurrence frequency for each type of sunspot group changes along the solar cycle development, which can be interpreted as the emerging and decaying process of sunspot groups is different depending on the phase of solar cycle. Therefore, it is considered that a following study would contribute to the efforts to understand the dependence of the dynamo mechanism on the phase of solar cycle.
413
- 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.
414
- 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.
415
- 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.
416
- Linnell, Albert P.
- Journal of astronomy and space sciences
- 29, n.2
- pp.123-129
- 2012
- 원문 바로보기
The BINSYN program package, recently expanded to calculate synthetic spectra of cataclysmic variables, is being further extended to include synthetic photometry of ordinary binary stars in addition to binary stars with optically thick accretion disks. The package includes a capability for differentials correction optimization of eclipsing binary systems using synthetic photometry.
417
- Hwang, Junga
- Journal of astronomy and space sciences
- 29, n.4
- pp.329-336
- 2012
- 원문 바로보기
Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Bohyunsan Observatory to measure the Earth's magnetic field variations in South Korea. In 2007, we installed a fluxgate magnetometer (RFP-523C) to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we use the H, D, Z components of fluxgate magnetometer data to investigate the characteristics of mid-latitude geomagnetic field variation. To remove the temporary changes in Earth's geomagnetic filed by space weather, we use the international quiet days' data only. In other words, we performed a superposed epoch analysis using five days per each month during 2008-2011. We find that daily variations of H, D, and Z shows similar tendency compared to previous results using all days. That is, H, D, Z all three components' quiet intervals terminate near the sunrise and shows maximum 2-3 hours after the culmination and the quiet interval start from near the sunset. Seasonal variations show similar dependences to the Sun. As it becomes hot season, the geomagnetic field variation's amplitude becomes large and the quiet interval becomes shortened. It is well-known that these variations are effects of Sq current system in the Earth's atmosphere. We confirm that the typical mid-latitude geomagnetic field variations due to the Sq current system by excluding all possible association with the space weather.
418
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.
419
- 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.
420
- 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.