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1968년 ~ 2023년까지 1,187 건의 한국천문학회지를 격월간 확인하실 수 있습니다.
- The Korean Astronomical Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-4614 (ISSN : 1225-4614)
1225-4614
- DB구축현황 : 1,187건 (DB Construction : 1,187 Articles)
총 게시글 1,187건
페이지 71/119
701
- 김강민
- Journal of the Korean astronomical society = 천문학회지
- 34, n.1
- pp.41-45
- 2001
- 원문 바로보기
We tested the characteristics of the BOAO Medium Dispersion Spectrograph (MDS) such as the CCD capabilities, wavelength shift by gravity direction variation, slit illumination function and efficiency. Then we calculated the appropriate exposure time to obtain the given S/N ratio for several given magnitudes. Also the remaining problems to be improved were discussed.
702
- PARK KYUNG SUN
- Journal of the Korean astronomical society = 천문학회지
- 34, n.4
- pp.317-319
- 2001
- 원문 바로보기
The response of the earth's magnetosphere to the variation of the solar wind parameters and Interplanetary magnetic field (IMF) has been stud}ed by using a high-resolution, three-dimension magnetohydrodynamic (MHD) simulation when the WIND data of velocity Vx, plasma density, dynamic pressure, By and Bz every 1 minute were used as input. Large electrojet and magnetic storm which occurred on October 21 and 22 are reproduced in the simulation (fig. 1). We have studied the energy transfer and tail reconnect ion in association with geomagnetic storms.
703
- KIM JONGSOO
- Journal of the Korean astronomical society = 천문학회지
- 34, n.4
- pp.281-283
- 2001
- 원문 바로보기
As a companion to an adiabatic version developed by Ryu and his coworkers, we have built an isothermal magnetohydrodynamic code for astrophysical flows. It is suited for the dynamical simulations of flows where cooling timescale is much shorter than dynamical timescale, as well as for turbulence and dynamo simulations in which detailed energetics are unimportant. Since a simple isothermal equation of state substitutes the energy conservation equation, the numerical schemes for isothermal flows are simpler (no contact discontinuity) than those for adiabatic flows and the resulting code is faster. Tests for shock tubes and Alfven wave decay have shown that our isothermal code has not only a good shock capturing ability, but also numerical dissipation smaller than its adiabatic analogue. As a real astrophysical application of the code, we have simulated the nonlinear three-dimensional evolution of the Parker instability. A factor of two enhancement in vertical column density has been achieved at most, and the main structures formed are sheet-like and aligned with the mean field direction. We conclude that the Parker instability alone is not a viable formation mechanism of the giant molecular clouds.
704
- 이용삼
- Journal of the Korean astronomical society = 천문학회지
- 34, n.1
- pp.47-57
- 2001
- 원문 바로보기
In this paper we have reconstructed an armillary sphere based on the Method of an Armillary Sphere Making described in the Volume 1 of The Collection of Writings on the Scientific Instruments-Uigijipsol (儀器輯說, two volumes) edited in the 1850's by Nam Byong-Chul (南秉哲, 1817-1863) who was a famous Korean states-man-scientist. Nam achieved convenience and accuracy in the measurements of stellar positions in the manner of selective setting the equatorial, ecliptic and horizontal poles by adding a pole axis exchange ring called Jaigeukkwon (載極圈) between the Three Arrangers of Time and Four Displacements. We made use of 3-dimensional graphic software for modelling Nam's armillary sphere which consisted of five layers-eight rings. Results of simulation showed that the pole axis exchange ring functioned properly in setting the equatorial, ecliptic and horizontal coordinates simply by exchange of positions of specified holes on the ring. We ascertained that the invention of Jaigeukkwon solved inherent problems in the conventional Chinese armillary sphere in computation of real ecliptic coordinates. It was revealed that Nam Byong-Chul made great contributions in the East Asian history of armillary sphere making.
705
- BALSARA DINSHAW
- Journal of the Korean astronomical society = 천문학회지
- 34, n.4
- pp.181-190
- 2001
- 원문 바로보기
The advent of robust, reliable and accurate higher order Godunov schemes for many of the systems of equations of interest in computational astrophysics has made it important to understand how to solve them in multi-scale fashion. This is so because the physics associated with astrophysical phenomena evolves in multi-scale fashion and we wish to arrive at a multi-scale simulational capability to represent the physics. Because astrophysical systems have magnetic fields, multi-scale magnetohydrodynamics (MHD) is of especial interest. In this paper we first discuss general issues in adaptive mesh refinement (AMR), We then focus on the important issues in carrying out divergence-free AMR-MHD and catalogue the progress we have made in that area. We show that AMR methods lend themselves to easy parallelization. We then discuss applications of the RIEMANN framework for AMR-MHD to problems in computational astophysics.
706
- KIM HUN-DAE
- Journal of the Korean astronomical society = 천문학회지
- 34, n.3
- pp.167-179
- 2001
- 원문 바로보기
A molecular line survey towards the UC H II region G34.3+0.15 from 155.3 to 165.3GHz has been conducted with the TRAO 14-m radio telescope. Combined with our previous observations from 84.7 to 115.6GHz and 123.5 to 155.3GHz (Paper I), the spectral coverage of this survey in G34.3+0.15 now runs from 85 to 165 GHz. From these latest observations, a total of 18 lines from 6 species were detected. These include four new lines corresponding to <TEX>${\Delta}$</TEX>J = 0, <TEX>${\Delta}$</TEX>K = 1 transitions of the <TEX>$CH_3OH$</TEX> E-type species, and two new lines corresponding to transitions from <TEX>$SO_2$</TEX> and <TEX>$HC_3N$</TEX>. These 6 new lines are <TEX>$CH_3OH$</TEX>[1(1) - 1(0)E], <TEX>$CH_3OH$</TEX>[2(1) - 2(0)E], <TEX>$CH_3OH$</TEX>[3(1) - 3(0)E], <TEX>$CH_3OH$</TEX>[4(1) - 4(0)E], <TEX>$SO_2$</TEX>[14(1, 13) -14(0, 14)] and <TEX>$HC_3N$</TEX>[18 -17]. We applied a rotation diagram analysis to derive rotation temperatures and column densities from the methanol transitions detected, and combined with NRAO 12-m data from Slysh et al. 1999. Applying a two-component fit, we find a cold component with temperature 13-16K and column density <TEX>$3.3-3.4 {\times} 10^{14} cm^{-2}$</TEX>, and a hot component with temperature 64 - 83K and column density <TEX>$9.3{\times}10^{14} - 9.7 {\times} 10^{14} cm^{-2}$</TEX>. On the other hand, applying just a one-component fit yields temperatures in the 47 -62 K range and column densities from <TEX>$7.5-1.1 {\times} 10^{15} cm^{-2}$</TEX>.
707
- 문봉곤
- Journal of the Korean astronomical society = 천문학회지
- 34, n.1
- pp.35-40
- 2001
- 원문 바로보기
For the planned experiments of Korea Sounding Rocket-III (KSR-III), we have constructed a model of MUV dayglow in the mid-latitude. The model computes relative intensities of individual emission lines in the Vegard-Kaplan and 2PG band systems of <TEX>$N_2$</TEX> in the wavelength range of 2500-3500<TEX>${\AA}$</TEX>. In addition to the emission lines, solar scattered continuum was computed by an extended LOWTRAN7 code, in which we have included solar scattering in altitudes higher than 100 km by using MSIS90 thermosphere model. Ratios among vibrational bands of VK and 2PG system, were computed from the observed MUV dayglow spectra of Cleary et al. (1995). The model provides MUV dayglow intensitiy profiles with a wavelength resolution of 3.13<TEX>${\AA}$</TEX> as a function of altitude. The computed intensity profiles have been utilized in designing the KSR-III airglow photometers.
708
- 한수련
- Journal of the Korean astronomical society = 천문학회지
- 34, n.2
- pp.67-80
- 2001
- 원문 바로보기
Chemical evolution of galaxies can be understood by studying the spatial distribution of heavy elements. We selected two nearby galaxies, M31 and M33 and investigated spectrum of their HII regions: a) the elec-tron densities have been derived from the [S II] 6717/6731 ratio along with the most recent atomic constants (Hyung & Aller 1996); b) the electron temperatures were determinated from the Pagel's empirical method. Nebula Model (Hyung 1994) has been employed to predict the spectral line intensities which gives the proper chemical abundances. The model would predict the line intensities correctly only when various input parameters such as the effective central star temperatures, gravity log g, model atmosphere as well as the geometry and the nebula physical condition are appropriate. Thus, the determination of chemical abundances of O, S, N of the two nearby galaxies M31 and M33 has been done, which shows a radial dependance of O/H and N/H: decrease with the distance, or increasing electron temperature due to the elemental deficiency. Abundances of M31 appear to be enhanced than those of M33.
709
- KOVALENKO ILYA G.
- Journal of the Korean astronomical society = 천문학회지
- 34, n.4
- pp.271-273
- 2001
- 원문 바로보기
We present a 4-parameter implicit Lagrangean code which satisfies conservation of mass, linear and angular momenta, energy and entropy simultaneously. The primary advantage of this scheme is possibility to control dissipative properties of the scheme avoiding the effects of numerical viscosity.
710
- MATHEWS GRANT J.
- Journal of the Korean astronomical society = 천문학회지
- 34, n.4
- pp.265-269
- 2001
- 원문 바로보기
We present preliminary numerical simulations of tilted-disk accretion around a rotating black hole. Our goal is to explore whether hydrodynamic instabilities near the Bardeen-Petterson radius could be responsible for generating moderate-frequency quasi-periodic oscillations in X-ray binaries. We review the relevant general relativistic hydrodynamic equations, and discuss preliminary results on the structure and dynamics of a thin, Keplerian disk.