• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.83-92
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• 2004

The absolute dimensions of low mass contact binary, GR Vir and HV Aqr were obtained using WD program from the published spectroscopic and photometric observational data. The evolutionary status of this type of system including GR Vir and HV Aqr has been considered. The primary stars of low mass contact binary system were located on the Terminal Age Main-sequence and secondary stars were located under the Zero Age Main-sequence in H-R diagram.

• Journal of Astronomy and Space Sciences
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• v.29 no.2
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• pp.145-149
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• 2012

I describe a series of processes, including hierarchical fragmentation, gravitational scattering, Kozai cycles within triple systems, tidal friction and magnetic braking, that I believe are responsible for producing the modest but significant fraction of stars that are observed as contact binaries. I also discuss further processes, namely heat transport, mass transport, nuclear evolution, thermal relaxation oscillations, and further magnetic braking with tidal friction, that influence the evolution during contact. The endpoint, for contact, is that the two components merge into a single star, as recently was observed in the remarkable system V1309 Sco. The single star probably throws off some mass and rotates rapidly at first, and then slows by magnetic braking to become a rather inconspicuous but normal dwarf or subgiant. If however the contact binary was part of a triple system originally-as I suggested above was rather likely-then the result could be a $widish$ binary with apparently non-coeval components. There are several such known.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.493-504
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• 2004

The history books of East Asia about astronomical phenomena have the more records of the solar eclipse frequently than any other ones. It is because traditionally, the solar eclipse moaned the fate of dynasty and the king's rule. The Sun, the biggest thing in the heaven symbolized the king, and the solar eclipse foresaw that the king had the problem in private including the body, and the country might suffer from difficulties in a great scale. So the king and all of the ministers used to gather to hold a ceremony named Gusikrye(구식례) which solar eclipse may pass safely. Consequently, kings always had concernments on collecting informations of solar eclipse. Inspite of importance of solar eclipse predictions, but at the beginning of the Choseon, the predictions of the solar eclipse didn't fit. King Sejong compiled the Chiljeongsan-naepion (칠정산내편) and the Chiljeongsan-oepyeon(칠정산외편) to calculate the celestial phenomena including the solar eclipse. By the publications of these two books, the calendar making system of Choseon was firmly established. The Chiljeongsan-oepyeon adopted Huihui calendar(회회력) of Arabia. The Solar eclipse predictions of Chiljeongsan-oepyeon were relative correct compared to modern method in early Choseon dynasty.

• Journal of Astronomy and Space Sciences
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• v.19 no.2
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• pp.107-122
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• 2002

Multi-body spacecraft attitude and configuration control formulations based on the use of collaborative control theory are considered. The control formulations are based on two-player, nonzero-sum, differential game theory applied using a Nash strategy. It is desired that the control laws allow different components of the multi-body system to perform different tasks. For example, it may be desired that one body points toward a fixed star while another body in the system slews to track another satellite. Although similar to the linear quadratic regulator formulation, the collaborative control formulation contains a number of additional design parameters because the problem is formulated as two control problems coupled together. The use of the freedom of the partitioning of the total problem into two coupled control problems and the selection of the elements of the cross-coupling matrices are specific problems ad-dressed in this paper. Examples are used to show that significant improvement in performance, as measured by realistic criteria, of collaborative control over conventional linear quadratic regulator control can be achieved by using proposed design guidelines.

• Journal of Astronomy and Space Sciences
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• v.31 no.2
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• pp.121-130
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• 2014

Essential ideas, successes, and difficulties of Areal Density Analysis (ADA) for color-magnitude diagrams (CMD's) of resolved stellar populations are examined, with explanation of various algorithms and strategies for optimal performance. A CMD-generation program computes theoretical datasets with simulated observational error and a solution program inverts the problem by the method of Differential Corrections (DC) so as to compute parameter values from observed magnitudes and colors, with standard error estimates and correlation coefficients. ADA promises not only impersonal results, but also significant saving of labor, especially where a given dataset is analyzed with several evolution models. Observational errors and multiple star systems, along with various single star characteristics and phenomena, are modeled directly via the Functional Statistics Algorithm (FSA). Unlike Monte Carlo, FSA is not dependent on a random number generator. Discussions include difficulties and overall requirements, such as need for fast evolutionary computation and realization of goals within machine memory limits. Degradation of results due to influence of pixelization on derivatives, Initial Mass Function (IMF) quantization, IMF steepness, low Areal Densities ($\mathcal{A}$), and large variation in $\mathcal{A}$ are reduced or eliminated through a variety of schemes that are explained sufficiently for general application. The Levenberg-Marquardt and MMS algorithms for improvement of solution convergence are contained within the DC program. An example of convergence, which typically is very good, is shown in tabular form. A number of theoretical and practical solution issues are discussed, as are prospects for further development.

• Journal of Astronomy and Space Sciences
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• v.35 no.2
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• pp.67-74
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• 2018

Higgs boson enables the Standard Model (SM) to be established. However, we do not know much about dark matter which occupies approximately six times of the SM particles in universe besides having mass. The interactions of dark matter is much weaker than that of the SM. Further, its mass range is very wide, from the order of eV to PeV. Therefore, many experiments have contributed to search for dark matter by indirect, direct and accelerator research. This paper reviews researches on dark matter using accelerator, especially the $e^+e^-$ collider, from the viewpoint of experimental high energy physicists.

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.13-19
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• 2015

Plasma bubbles that occur in the equatorial F-region make up one of the most distinguishing phenomena in the ionosphere. Bubbles represent plasma depletions with respect to the background ionosphere, and are the major source of electron density irregularities in the equatorial F-region. Such bubbles are seen as plasma depletion holes (in situ satellite observations), vertical plumes (radar observations), and emission-depletion bands elongated in the north-south direction (optical observations). However, no technique can observe the whole three-dimensional structure of a bubble. Various aspects of bubbles identified using different techniques indicate that a bubble has a "shell" structure. This paper reviews the development of the concepts of "bubble" and "shell" in this context.

• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.115-119
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• 2019

This paper is a part of the series on positron annihilation spectroscopy of two-phase diffuse gas-and-dust aggregates, such as interstellar medium and the young remnants of type II supernovae. The results obtained from prior studies were applied here to detect the relationship between the processes of the annihilation of the K-shell electrons and incident positrons, and the effects of these processes on the optical spectra of their respective atoms. Particular attention was paid to the Doppler broadening of their optical lines. The relationship between the atomic mass of the elements and the Doppler broadening, ${\Delta}{\lambda}_D$ (${\AA}$), of their emission lines as produced in these processes was established. This relationship is also illustrated for isotope sets of light elements, namely $^3_2He$, $^6_3Li$, $^7_3Be$, $^{10}_5B$ and $^{11}_5B$. A direct correlation between the ${\gamma}-line$ luminosity ( $E_{\gamma}=1.022MeV$) and ${\Delta}{\lambda}_D$ (${\AA}$) was proved virtually. Qualitative estimates of the structure of such lines depending on the positron velocity distribution function, f(E), were made. The results are presented in tabular form and can be used to set up the objectives of further studies on active galactic nuclei and young remnants of type II supernovae.

• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.397-404
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• 2006

Geometric singularity problems are principle difficulties of single-gimbal control moment gyros in spacecraft attitude control. To overcome these singularities, many steering logics have been studied. In this paper, a new null motion steering law is suggested, which is based on the minimization of the directional components of output torque with respect to the required torque. The suggested steering law has been simulated and verified to work well around several critical singular points which have been classified as testing points of avoidance algorithm in previous literatures.

• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.403-416
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• 2003

There are common features, in both imaging surveys and image processing, between astronomical observations and remote sensing. Handling large amounts of data, in an easy and fast way, has become a common issue. Implementing pipeline software can be a solution to the problem, one which allows the processing of various kinds of data automatically. As a case study, the development of pipeline software for the EIS (European Southern Observatory Imaging Survey) is introduced. The EIS team has been conducting a sky survey to provide candidate targets to the 250 VLTs (Very Large Telescopes) observations. The survey data have been processed in a sequence of five major data corrections and reductions, i.e. preprocessing, flat fielding, photometric and astrometric corrections, source extraction, and coaddition. The processed data are eventually distributed to the users. In order to provide automatic processing of the vast volume of observed data, pipeline software has been developed. Because of the complexity of objects and different characteristic of each process, it was necessary to analyze the whole works of the EIS survey program. The overall tasks of the EIS are identified, and the scheme of the EIS pipeline software is defined. The system structure and the processes are presented, and in-depth flow charts are analyzed. During the analyses, it was revealed that handling the data flow and managing the database are important for the data processing. These analyses may also be applied to many other fields which require image processing.