• Journal of Astronomy and Space Sciences
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• v.35 no.2
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• pp.83-92
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• 2018

The summer polar lower thermosphere (90-100 km) has an interesting connection to meteors, adjacent to the mesopause region attaining the lowest temperature in summer. Meteors supply condensation nuclei for charged ice particles causing polar mesospheric summer echoes (PMSE). We report the observation of meteor trail with nearly horizontal transit at high speed (20-50 km/s), and at last with re-enhanced echo power followed by diffusive echoes. Changes in phase difference between radar receivers aligned in meridional and zonal directions are used to determine variations in horizontal displacements and speeds with respect to time by taking advantage of radar interferometric analysis. The actual transit of echo target is observed along the straight pathway vertically and horizontally extended as much as a distance of at least 24 km and at most 29 km. The meteor trail initially has a signature similar to 'head echoes', with travel speeds from 20 - 50 km/s. It subsequently transforms into a different type of echo target including specular echo and then finally the power reenhanced. The reenhancement of echo power is followed by fume-like diffusive echoes, indicating sudden release of plasma as like explosive process probably involved. We discuss a possible role of meteor-triggered secondary plasma trail, such as fireball embedded with electrical discharge that continuously varies the power and transit speed.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.29.4-30
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• 2010

A VHF meteor radar at King Sejong Station ($162.22^{\circ}S$, $58.78^{\circ}W$), Antarctica has been observing meteors during a period of March 2007-July 2009. We analyzed the height profiles of the observed meteor decay times between 70 and 95 km by classifying strong and weak meteors according to their estimated electron line densities. The height profiles of monthly averaged decay times show a peak whose altitude varies with season in the range of 80~85 km: higher peak in southern spring and summer than in fall and winter. The higher peak during summer is consistent with colder temperatures that cause faster chemical reactions of electron removal, as effective recombination rates measured by rocket experiments. The height profiles of 15-min averaged decay times show a clear increasing trend with decreasing altitude from 95 km to the peak altitude, especially for weak meteors. This feature for weak meteors is well explained by ambipolar diffusion of meteor trails, allowing one to estimate atmospheric temperatures and pressures, as in previous studies. However, the strong meteors show not only significant scatters but also different slope of the increasing trend from 95 km to the peak altitude. Therefore, atmospheric temperature estimation from meteor decay times should be applied for weak meteors only. In this study, we present the simple model decay times to explain the height profiles of the observed decay times and discuss the additional removal processes of meteor trail electrons through the empirical recombination and by icy particles.

• The Bulletin of The Korean Astronomical Society
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• v.34 no.1
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• pp.88-88
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• 2009

• The Bulletin of The Korean Astronomical Society
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• v.34 no.1
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• pp.87-87
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• 2009

• The Journal of Society for e-Business Studies
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• v.10 no.3
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• pp.85-110
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• 2005

OWL-S has a major leadership in the field of Web Service discovery and is being actively studied in LARKS and METEOR-S projects. These researches do not consider all components of OWL-S standards, and it is needed to enhance their discovery algorithms. In this paper, we propose matching algorithms based on process information such as process structure matching, service classification matching and business pattern matching algorithms. We also improve the QoS matching algorithm of METEOR-S project. Finally, we integrate these two kinds of matching algorithms as accommodate users preferences.

• The Bulletin of The Korean Astronomical Society
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• v.27 no.1
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• pp.36-36
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• 2002

Everyday meteors can be classified into sporadic meteors and shower-meteors. We compile the meteor records in the astronomical archives in the history book of Koryo dynasty (Koryosa), and investigate the spatial distribution of meteories along the orbit of the Earth during the period between the 10th century and the 14th century. We discover several peaks in cumulative frequency of meteors excluding showers, which means the presence of the strong concentrations of meteorites at the ecliptic longitudes. We also compiled the whole records of meteor showers during the same period from the history books of Korean, Japan, and China, and then compare dates of their display with dates obtained in Koryosa archive. Especially the strong concentration at 27 July is exactly coincident with a meteor shower at the same date. We devide the data into two sets, which are before and after 1200 A.D., and find out that the strength of meteor concentration has been changing. Especially the shower at 27 July weaken as time goes by.

• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.283-298
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• 2003

The 2001 Leonid meteor storm has been observed all over the world, and its most intense flux since the last few decades has caused great interest among both laymen and experts. Especially, its maximum hours occurred at dawn hours of Nov. 19 in the east Asia, during which moonless clear night at the Mt. Bohyun allowed us near perfect condition of observation. Observation was carried out in the period of 01:00∼05:40(KST), which include the predicted maximum hours, with all-sky camera installed for upper atmospheric airglow research. Tn this paper we analyze 68 all-sky images obtained in this period, which contain records of 172 meteors. Utilizing the zenith hourly rate(ZHR) of 3000 and magnitude distribution index of 2, which were reported to International Meteor Organization by visible observers in the east Asia, we estimate the limiting magnitude of about 3 for meteors detected in our all-sky images. We then derive magnitudes of 83 meteors with clear pixel brightness outlines among the initially detected 172 meteors by comparing with neighbor standard stars. Angular velocities of meteors needed for computing their passing times over an all-sky image are expressed with a simple formula of an angle between a meteor head and the Leonid radiant point. The derived magnitudes of 83 meteors are in the range of -6∼-1 magnitude, and its distribution shows a maximum new -3mag. The derived magnitudes are much smaller than the limiting magnitude inferred from the comparison with the result of naked-eye observations. The difference may be due to the characteristic difference between nearly instantaneuous naked-eye observations and CCD observations with a long exposure. We redetermine magnitudes of the meteors by adjusting a meteor lasting time to be consistent with the naked-eye observations. The relative distribution of the redetermined magnitudes, which has a maximum at 0 mag., resembles that of the magnitudes determined with the in-principle method. The relative distribution is quite different from ones that decrease monotonically with decreasing magnitudes for meteors(1∼6) sensitive to naked-eye observations. We conclude from the magnitude distribution of our all-sky observation that meteors brighter than about 0 mag., appeared more frequently during the 2001 Leonid maximum hours. The frequent appearance of bright meteors has significantly important implication for meteor research. We noted, however, considerably large uncertainties in magnitudes determined only by comparing standard stars due to the unknown lasting time of meteors and the non-linear sensitivity of all-sky camera.

• Bulletin of the Korean Space Science Society
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• 2009.04a
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• pp.43.1-43.1
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• 2009

• Bulletin of the Korean Space Science Society
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• 2009.04a
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• pp.43.2-43.2
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• 2009

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.359-361
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• 1996