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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 37/125
361
- 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%).
362
- 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.
363
- Chung, Moon-Hee
- Journal of astronomy and space sciences
- 30, n.4
- pp.345-353
- 2013
- 원문 바로보기
A W-band Orthomode Transducer (OMT) has been developed for Korean VLBI Network (KVN) polarization observation. The OMT design was based on E-plane split-block technique using septum structure. 3-dimensional electromagnetic simulation was fully employed to optimize the performance of the OMT. Measurements of the fabricated OMT show that the return losses for the vertically and horizontally polarized modes are better than -20 dB across 80 ~ 108 GHz and the insertion losses for the both modes are less than 0.47 dB. The cross-polarization level of the OMT is less than -30 dB. The bandwidth of the developed OMT is estimated as around 30%.
364
- 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.
365
- 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.
366
- Na, Sung-Ho
- Journal of astronomy and space sciences
- 30, n.1
- pp.33-41
- 2013
- 원문 바로보기
Various features of the existing perturbations in the Earth's spin rotation are investigated for the recent and most reliable data by spectral analysis, filtering, and comparison with idealized model. First, theory of Earth's spin rotational perturbation is briefly re-derived in the Earth-fixed coordinate frame. By spectral windowings, different periodic components of the length of day perturbation are separated, and their characters and excitations are discussed. Different periodic components of polar motion are acquired similarly and described with further discussion of their excitations. Causes of the long time trends of both the length of day and polar motion are discussed. Three possible causes are considered for the newly discovered 490-day period component in the polar motion.
367
- Hu, Chin-Ping
- Journal of astronomy and space sciences
- 30, n.2
- pp.79-82
- 2013
- 원문 바로보기
We present the Hilbert-Huang transform (HHT) analysis on the quasi-periodic modulation of SMC X-1. SMC X-1, consisting of a neutron star and a massive companion, exhibits superorbital modulation with a period varying between ~40 d and ~65 d. We applied the HHT on the light curve observed by the All-Sky Monitor onboard Rossi X-ray Timing Explorer (RXTE) to obtain the instantaneous frequency of the superorbital modulation of SMC X-1. The resultant Hilbert spectrum is consistent with the dynamic power spectrum while it shows more detailed information in both the time and frequency domains. According to the instantaneous frequency, we found a correlation between the superorbital period and the modulation amplitude. Combining the spectral observation made by the Proportional Counter Array onboard RXTE and the superorbital phase derived in the HHT, we performed a superorbital phase-resolved spectral analysis of SMC X-1. An analysis of the spectral parameters versus the orbital phase for different superorbital states revealed that the diversity of <TEX>$n_H$</TEX> has an orbital dependence. Furthermore, we obtained the variation in the eclipse profiles by folding the All Sky Monitor light curve with orbital period for different superorbital states. A dip feature, similar to the pre-eclipse dip of Her X-1, can be observed only in the superorbital ascending and descending states, while the width is anti-correlated with the X-ray flux.
368
- Nam, Uk-Won
- Journal of astronomy and space sciences
- 30, n.2
- pp.107-112
- 2013
- 원문 바로보기
Tissue equivalent proportional counter (TEPC) can measure the Linear Energy Transfer (LET) spectrum and calculate the equivalent dose for the complicated radiation field in space. In this paper, we developed and characterized a TEPC for radiation monitoring in International Space Station (ISS). The prototype TEPC which can simulate a 2 <TEX>${\mu}m$</TEX> of the site diameter for micro-dosimetry has been tested with a standard alpha source (<TEX>$^{241}Am$</TEX>, 5.5 MeV). Also, the calibration of the TEPC was performed by the <TEX>$^{252}Cf$</TEX> neutron standard source in Korea Research Institute of Standards and Science (KRISS). The determined calibration factor was <TEX>$k_f=3.59{\times}10^{-7}$</TEX> mSv/R.
369
- Kim, Sang Hyuk
- Journal of astronomy and space sciences
- 30, n.2
- pp.113-121
- 2013
- 원문 바로보기
Heumgyeonggaknu is a water-hammering type automatic water clock which was made by Jang Yeong-Sil in 1438. The water clock that is located in Heumgyeonggaknu consists of Suho which is equipped with 2-stage overflow. Constant water wheel power is generated by supplying a fixed amount of water of Suho to Sususang, and this power is transferred to each floor at the same time. The 1st floor rotation wheel of Gasan consists of the operation structure which has the shape of umbrella ribs. The 2nd floor rotation wheel is made so that the 12 hour signal, Gyeong-Jeom signal, and Jujeon constitute a systematic configuration. The 3rd floor rotation wheel is made so that the signal and rotation of Ongnyeo and four gods can be accomplished. Based on the above conceptual design, this paper analyzed the internal signal generation and power transmission of Heumgyeonggaknu.
370
- 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.