• Bulletin of the Korean Mathematical Society
• /
• v.50 no.3
• /
• pp.801-809
• /
• 2013

In this paper, we construct nilpotent semigroups S such that $S^n=\{0\}$, $S^{n-1}{\neq}\{0\}$ and ${\Gamma}(S)$ is a refinement of the star graph $K_{1,n-3}$ with center $c$ together with finitely many or infinitely many end vertices adjacent to $c$, for each finite positive integer $n{\geq}5$. We also give counting formulae to calculate the number of the mutually non-isomorphic nilpotent semigroups when $n=5$, 6 and in finite cases.

• Journal of The Korean Astronomical Society
• /
• v.21 no.2
• /
• pp.155-171
• /
• 1988

We have examined how sensitively the extinction value determined by the method of star-count depends on such factors as the plate limit, the size of counting reseau, the non-linearity in the number distribution of stars with magnitude, and the angular resolution demanded by the given problem. We let the Poisson distribution portray the statistical nature of the countings, and chose the region containing the globule Barnard 361 as an example field. Uncertainties due to various combinations of the factors are presented in graphic forms: (1) Dynamic range in the extinction measurements is evaluated as a function of reseau size for varying plate limits. (2) Statistical errors involved in the star-count are analized in terms of the signal-to-noise ratio, the plate limit and the reseau size. (3) Systematic error due to the non-linearity in the number distribution are thoroughly analized. (4) Finally, a methodology is presented for correcting the systematic error in the observed radial density gradient. These graphs are meant to be used in selecting proper size of the reseau and in estimating errors inherent to the star-count analysis.

• Lingua Humanitatis
• /
• v.1 no.1
• /
• pp.185-194
• /
• 2001

In this paper, I propose that the figurative structure of Tongjoo Yoon′s "One Night, Counting the Stars" reflects the poet′s anguish over the colonial reality of Korea in the later stages of the Japanese occupation, especially regarding the forced adoption of Japanese names in 1939. The poet Yoon himself registered at Yonhi College with an adopted Japanese name. In the second half of the poem, the speaker alludes to this historical fact when he confesses that "On a hill lit by myriads of stars / I spelled my name / And covered it over with dirt," and that he "laments (his) shameful name." In the simile of the last stanza, the speaker continues to allude to the "buried" name: "But past winter, come spring to my star, / As green grass sprouts on a grave mound, / So will it spread with pride / On the hill where my name is buried." The longing and the yearning, expressed so simply and in child-like manner in the first half of the poem, become in the second half an urgent need for something that should have been but cannot be, and yet will be in the future-for a world that should be, now lost but to be regained. The poem contains the poet′s earnest belief that the inherited Korean names that were then so shamefully taken away will one day be recovered. It is almost impossible to find any other work written in Korean (despite the most suppressive measures against the use of the Korean language) that also alludes to the adoption of Japanese names. In this respect, "One Night, Counting the Stars" has a unique value in the history of modem Korean literature.

• Journal of The Korean Astronomical Society
• /
• v.46 no.6
• /
• pp.203-224
• /
• 2013

Wide-field $JHK_s$ images obtained with the SIRIUS near-infrared camera of the IRSF 1.4m telescope are used to examine the tidal structures of the spatial stellar configuration around six metal-poor ([Fe/H]< -1.0) globular clusters located within 3 kpc from the Galactic center. The radial surface density profiles are obtained from the surface photometry of the cluster images and the star counting for the photometric data. For the star counting, candidates of cluster member stars are selected with an filtering algorithm in color-magnitude diagrams. We find that the six target clusters show tidal overdensity features in the radial surface density profiles. There is a break inside the tidal radius for each cluster, and the profile in the outer overdensity region is characterized by a power law. Two-dimensional density maps of all the clusters show distorted asymmetric stellar configurations in the outer region. In five out of the six target clusters, the overdensity features are likely to be associated with the effects of the Galaxy dynamical interaction and the cluster space motions. The observed tidal configurations of stars suggest that several metal-poor clusters in the Galactic bulge are possibly surviving remnants of mergers to build the old stellar system of the Galactic bulge.

• Publications of The Korean Astronomical Society
• /
• v.16 no.1
• /
• pp.43-47
• /
• 2001

We developed a CCD camera that can observe wide fields on the sky. We tested the field of views using various lenses. For cooling the CCD chip, we used a thermoelectric cooling device and tested the cooling efficiency. This camera will continuously observe a part of the sky. The data from the camera will be used to decide the current weather condition by the real-time star counting program (SCount) which will be developed later.

• Journal of The Korean Astronomical Society
• /
• v.24 no.1
• /
• pp.107-116
• /
• 1991

With a modern microdensitometer and POSS glass copies, we have performed an automated star counting in two colors, blue and red, over the region containing Bok globule B361. Distribution of the measured extinction values over the projected angular distance from the cloud center was approximated by a power-law, and the resulting power-law indices for the blue and red are shown to be distinctly different from each other. The difference in the power-law index indicates that the mean dust size increases towards the cloud center. Possible physical causes for such size variation are briefly discussed.

• Journal of Satellite, Information and Communications
• /
• v.8 no.3
• /
• pp.32-40
• /
• 2013

The Boltwood Cloud Sensor is meteorological sensor that is used to estimate an amount of clouds in the sky. This sensor will be installed for OWL(Optical Wide-field patroL) telescope and observatory system of Korea Astronomy and Space Science. Before applying this sensor to an observatory system, we performed test observations at Chungbuk University Observatory at Jincheon, Chungbuk. During the test run, a significant correlation between air temperature difference and the number of visible stars recorded in the CCD frames has not been found. This preliminary result can be attributed to test environment of the observation and our lack of knowledge on calculation algorithm as well as the hardware system of the Boltwood Cloud Sensor.In this paper, we present the procedure and the result of the performance test employing the cloud sensor.