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1984년 ~ 2025년까지 1,253 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 : 1,253건 (DB Construction : 1,253 Articles)
총 게시글 1,253건
페이지 37/126
361
- Harding, Alice K.
- Journal of astronomy and space sciences
- 30, n.3
- pp.145-152
- 2013
- 원문 바로보기
Rotation-powered pulsars are excellent laboratories for studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. Particle acceleration and high-energy emission from the polar caps is expected to occur in connection with electron-positron pair cascades. I will review acceleration and gamma-ray emission from the pulsar polar cap and associated slot gap. Predictions of these models can be tested with the data set on pulsars collected by the Large Area Telescope on the Fermi Gamma-Ray Telescope over the last four years, using both detailed light curve fitting, population synthesis and phase-resolved spectroscopy.
362
- Hwang, InYoung
- Journal of astronomy and space sciences
- 30, n.1
- pp.11-15
- 2013
- 원문 바로보기
A collision-free formation reconfiguration trajectory subject to the linearized Hill's dynamics of relative motion is analytically developed by extending an algorithm for gravity-free space. Based on the initial solution without collision avoidance constraints, the final solution to minimize the designated performance index and avoid collision is found, based on a gradient method. Simple simulations confirm that satellites reconfigure their positions along the safe trajectories, while trying to spend minimum energies. The algorithm is applicable to wide range of formation flying under the Hill's dynamics.
363
- Park, Jong-Hyeok
- Journal of astronomy and space sciences
- 30, n.4
- pp.241-246
- 2013
- 원문 바로보기
We have investigated drought periodicities occurred in Seoul to find out any indication of relationship between drought in Korea and solar activities. It is motivated, in view of solar-terrestrial connection, to search for an example of extreme weather condition controlled by solar activity. The periodicity of drought in Seoul has been re-examined using the wavelet transform technique as the consensus is not achieved yet. The reason we have chosen Seoul is because daily precipitation was recorded for longer than 200 years, which meets our requirement that analyses of drought frequency demand long-term historical data to ensure reliable estimates. We have examined three types of time series of the Effective Drought Index (EDI). We have directly analyzed EDI time series in the first place. And we have constructed and analyzed time series of histogram in which the number of days whose EDI is less than -1.5 for a given month of the year is given as a function of time, and one in which the number of occasions where EDI values of three consecutive days are all less than -1.5 is given as a function of time. All the time series data sets we analyzed are periodic. Apart from the annual cycle due to seasonal variations, periodicities shorter than the 11 year sunspot cycle, ~ 3, ~ 4, ~ 6 years, have been confirmed. Periodicities to which theses short periodicities (shorter than Hale period) may be corresponding are not yet known. Longer periodicities possibly related to Gleissberg cycles, ~ 55, ~ 120 years, can be also seen. However, periodicity comparable to the 11 year solar cycle seems absent in both EDI and the constructed data sets.
364
- Jun, Chae-Woo
- Journal of astronomy and space sciences
- 30, n.1
- pp.25-32
- 2013
- 원문 바로보기
We statistically investigated the properties of low-latitude Pi2 pulsations using Bohyun (BOH, Mlat = <TEX>$29.8^{\circ}$</TEX>, L = 1.35) ground magnetometer data in 2008. For this 1-year interval, 582 Pi2 events were identified when BOH was in the nightside from 1800 to 0600 local times. We found the following Pi2 characteristics. (1) The occurrence distribution of Pi2s is relatively constant in local times. (2) The Pi2 frequency varies in local times. That is, Pi2 pulsations in postmidnight sector had higher frequency than in premidnight sector. (3) Pi2 power in premidnight sector is stronger than in postmidnight sector. (4) Pi2 frequency has positive correlation with solar wind speed and AE index. (5) Pi2 power has not a clear correlation with solar wind parameters. This indicates that Pi2 power is not controlled by external sources. (6) It is found that the most probable-time between Pi2 onsets is <TEX>${\Delta}t$</TEX> ~ 37.5 min: This is interpreted to be the period between Pi2 pulsations when they occur cyclically. We suggest that <TEX>${\Delta}t$</TEX> ~ 37.5 min is the occurrence rate of reconnection of open field lines in the tail lobe.
365
- Seo, Kyoung-Ae
- Journal of astronomy and space sciences
- 30, n.2
- pp.87-90
- 2013
- 원문 바로보기
We have investigated the X-ray emission from the shock-heated plasma of the Galactic supernova remnant Kesteven 69 with XMM-Newton. Assuming the plasma is at collisional ionization equilibrium, a plasma temperature and a column absorption are found to be kT ~ 0.62 keV and <TEX>$N_H{\sim}2.85{\times}10^{22}\;cm^{-2}$</TEX> respectively by imaging spectroscopy. Together with the deduced emission measure, we place constraints on its Sedov parameters.
366
- Kwak, Younghee
- Journal of astronomy and space sciences
- 30, n.4
- pp.315-320
- 2013
- 원문 바로보기
Space geodetic techniques can be used to obtain precise shape and rotation information of the Earth. To achieve this, the representative combination solution of each space geodetic technique has to be produced, and then those solutions need to be combined. In this study, the representative combination solution of very long baseline interferometry (VLBI), which is one of the space geodetic techniques, was produced, and the variations in the position coordinate of each station during 7 years were analyzed. Products from five analysis centers of the International VLBI Service for Geodesy and Astrometry (IVS) were used as the input data, and Bernese 5.0, which is the global navigation satellite system (GNSS) data processing software, was used. The analysis of the coordinate time series for the 43 VLBI stations indicated that the latitude component error was about 15.6 mm, the longitude component error was about 37.7 mm, and the height component error was about 30.9 mm, with respect to the reference frame, International Terrestrial Reference Frame 2008 (ITRF2008). The velocity vector of the 42 stations excluding the YEBES station showed a magnitude difference of 7.3 mm/yr (30.2%) and a direction difference of <TEX>$13.8^{\circ}$</TEX> (3.8%), with respect to ITRF2008. Among these, the 10 stations in Europe showed a magnitude difference of 7.8 mm/yr (30.3%) and a direction difference of <TEX>$3.7^{\circ}$</TEX> (1.0%), while the 14 stations in North America showed a magnitude difference of 2.7 mm/yr (15.8%) and a direction difference of <TEX>$10.3^{\circ}$</TEX> (2.9%).
367
- Kang, Hyesung
- Journal of astronomy and space sciences
- 30, n.3
- pp.133-140
- 2013
- 원문 바로보기
Most of high energy cosmic rays (CRs) are thought to be produced by diffusive shock acceleration (DSA) at supernova remnants (SNRs) within the Galaxy. Fortunately, nonthermal emissions from CR protons and electrons can provide direct observational evidence for such a model and place strong constraints on the complex nonlinear plasma processes in DSA theory. In this study we calculate the energy spectra of CR protons and electrons in Type Ia SNRs, using time-dependent DSA simulations that incorporate phenomenological models for some wave-particle interactions. We demonstrate that the time-dependent evolution of the self-amplified magnetic fields, Alfv<TEX>$\acute{e}$</TEX>nic drift, and escape of the highest energy particles affect the energy spectra of accelerated protons and electrons, and so resulting nonthermal radiation spectrum. Especially, the spectral cutoffs in X-ray and <TEX>${\gamma}$</TEX>-ray emission spectra are regulated by the evolution of the highest energy particles, which are injected at the early phase of SNRs. Thus detailed understandings of nonlinear wave-particle interactions and time-dependent DSA simulations of SNRs are crucial in testing the SNR hypothesis for the origin of Galactic cosmic rays.
368
- Mao, Jirong
- Journal of astronomy and space sciences
- 30, n.3
- pp.141-143
- 2013
- 원문 바로보기
We propose jitter radiation and jitter self-Compton process in this work. We apply our model to the study of GRB prompt emission and GeV-emission. Our results can explain the multi-wavelength spectrum of GRB 100728A very well.
369
- Jeon, Jeheon
- Journal of astronomy and space sciences
- 30, n.4
- pp.335-344
- 2013
- 원문 바로보기
TRiplet Ionospheric Observatory-CubeSat for Ion, Neutron, Electron & MAgnetic fields (TRIO-CINEMA) is a CubeSat with 3.14 kg in weight and 3-U (<TEX>$10{\times}10{\times}30$</TEX> cm) in size, jointly developed by Kyung Hee University and UC Berkeley to measure magnetic fields of near Earth space and detect plasma particles. When a satellite is launched into orbit, it encounters ultra-high vacuum and extreme temperature. To verify the operation and survivability of the satellite in such an extreme space environment, experimental tests are conducted on the ground using thermal vacuum chamber. This paper describes the temperature control device and monitoring system suitable for CubeSat test environment using the thermal vacuum chamber of the School of Space Research, Kyung Hee University. To build the chamber, we use a general purpose thermal analysis program and NX 6.0 TMG program. We carry out thermal vacuum tests on the two flight models developed by Kyung Hee University based on the thermal model of the TRIO-CINEMA satellite. It is expected from this experiment that proper operation of the satellite in the space environment will be achieved.
370
- Lee, Min-Soo
- Journal of astronomy and space sciences
- 30, n.4
- pp.299-305
- 2013
- 원문 바로보기
Ganui-Dae, built in the reign of King Sejong, Joseon Dynasty, is a comprehensive observatory. It has various instruments for observation and time signal such as Ganui, Gyupyo(Gnomon), water-hammering type Honui and Honsang, and so on. Studying on Ganui-Dae has been focused on its location, history, criterion, etc, so far. However, studying on its external form and construction method has been conducted insufficiently. This study suggests the model for restoration of Ganui-Dae. The model is based on the analysis about external form of Ganui-Dae in various antique maps, and its construction method in those days.