• Journal of the Korean Mathematical Society
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• v.61 no.3
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• pp.445-459
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• 2024

In this paper, by establishing the direct method of moving planes for the fractional Laplacian system with positive-negative mixed powers, we obtain the radial symmetry and monotonicity of the positive solutions for the fractional Laplacian systems with positive-negative mixed powers in the whole space. We also give two special cases.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.33-33
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• 2003

A clear bipolar (negative/positive) signature in the Ey component was observed by the Cluster satellite in the magnetotail during a sudden impulse (si) on October 11, 2001 (day 284). During the interval of the negative perturbation in Ey, the magnetic field strength in Bx, a dominant magnetic field component, was nearly constant. However, the amplitude of Bx was strongly enhanced during the positive Ey perturbation. We suggest that the observed E and B field variations are due to outward/inward plasma motions, associated with expanded and then compressed magnetopause variations. We also observed quasi-periodic geomagnetic perturbations in the Pc5 band (∼1-6 mHz) at the low-latitude ground station Kakioka (L = 1.25) following the si event. They were highly correlated with the magnetic field perturbations at Cluster in the magnetotail (Xgse = ∼12 Re). We show that the source of these perturbations is the quasi-periodic solar wind pressure variations moving tailward.

• Journal of the Korean Mathematical Society
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• v.50 no.2
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• pp.275-306
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• 2013

For two positive integers $m$ and $n$, let $\mathcal{P}_n$ be the open convex cone in $\mathbb{R}^{n(n+1)/2}$ consisting of positive definite $n{\times}n$ real symmetric matrices and let $\mathbb{R}^{(m,n)}$ be the set of all $m{\times}n$ real matrices. In this paper, we investigate differential operators on the non-reductive homogeneous space $\mathcal{P}_n{\times}\mathbb{R}^{(m,n)}$ that are invariant under the natural action of the semidirect product group $GL(n,\mathbb{R}){\times}\mathbb{R}^{(m,n)}$ on the Minkowski-Euclid space $\mathcal{P}_n{\times}\mathbb{R}^{(m,n)}$. These invariant differential operators play an important role in the theory of automorphic forms on $GL(n,\mathbb{R}){\times}\mathbb{R}^{(m,n)}$ generalizing that of automorphic forms on $GL(n,\mathbb{R})$.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.84.1-84.1
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• 2011

In this study, we intend to inquire of how the temporal variation and spatial distribution of magnetic helicity injection in a CME-producing solar active region are related to the CME occurrence. We therefore investigate long-term (a few days) variation of magnetic helicity injection in the active region NOAA 9236 which produced multiple CME events. As a result, it is found that a noticeable increase in helicity of negative sign was first made for the first ~1.5 days and then 6 CMEs occurred while the relatively more injection of oppositely signed (positive) helicity was taking place for the next ~2 days. Afterwards, 2 CMEs in the region occurred while a more negative helicity is being injected again compared to a positive helicity. In addition, from helicity flux density maps, we found that the CMEs originated from this active region seem to be involved with the interaction of two magnetic field systems characterized by opposite signs of helicity.

• Bulletin of the Korean Mathematical Society
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• v.41 no.2
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• pp.235-239
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• 2004

Vaughan proved that if X is countably compact, then the Alexandroff duplicate A(X) is acc. In this note, we give an example to show that the result can not be generalized to star-Lindelof spaces. Moreover, we give a positive result.

• Honam Mathematical Journal
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• v.23 no.1
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• pp.29-39
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• 2001

Let $\mathcal{B}$ be a Banach space of analytic functions defined on the open unit disk. Assume S is a bounded operator defined on $\mathcal{B}$ such that S is in the commutant of $M_zn$ or $SM_zn=-M_znS$ for some positive integer n. We give necessary and sufficient condition between compactness of $SM_z+cM_zS$ where c = 1, -1, i, -i, and the structure of S. Also we characterize the commutant of $M_zn$ for some positive integer n.

• Journal of the East Asian Society of Dietary Life
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• v.20 no.5
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• pp.812-822
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• 2010

This study explored choice attributes in specially coffee shops and examined the relations between choice attributes and positive emotions customers felt in specially coffee shops. The study also attempted to find differences in choice attributes and positive emotions according to general characteristics of customers and coffee-drinking behavior. Measured items were derived from preliminary interviews and a literature review. Questionnaires were distributed to customers in Seoul who had visited a specially coffee shop in the last 3 months. The derived factors of choice attributes were 'taste of coffee and atmosphere', 'brand', 'price benefit', 'pleasant space', and 'coffee itself. Among those, the two factors 'taste of coffee and atmosphere', and 'brand' had a statistically significant influence on positive emotions of customers. This implies that specially coffee shop customers have primarily emotional rather than utilitarian motivations. Therefore, to better satisfy customers' desires, more effort is needed to improve the physical environment in coffee shops. Female and younger customers showed higher perception of price benefits than others did. The perception of price benefits and pleasant space mainly varied by the location of coffee-drinking and frequency of visiting specially coffee shops. Further differences in positive emotion according to general characteristics and behaviors of having coffee also discussed.

• Journal of the Korean Society of Earth Science Education
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• v.5 no.3
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• pp.297-306
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• 2012

The purpose of this study was to examine the effects of science-based STEAM astronomical learning program on space perception ability and scientific attitudes. For this study the 5 grade, 2 class was divided into a research group and a comparative group. The class was pre-tested in order to ensure the same standard. Space perception ability test and scientific attitudes test was used to find the effect of the science-based steam astronomical learning program. And the results were analyzed by spsswin 18.0. The results of this study were as follows. First, the science-based STEAM astronomical learning program was a positive effects on space perception ability of elementary students. Second, the science-based STEAM astronomical learning program was a positive effects on scientific attitudes of elementary students. According to this research, the science-based STEAM astronomical learning program was verified to improve space perception ability and scientific attitudes on the elementary students.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.34.4-35
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• 2009

We have studied the radial g-r color gradients of early-type galaxies in the Sloan Digital Sky Survey (SDSS) DR6 in the redshift range 0.00 < z < 0.06. The color profiles of ~30 per cent of the galaxies in this sample show positive color gradients (centers being bluer). These positive gradient galaxies often show strong $H\beta$ absorption line strengths or emission line ratios that are consistent with star-forming populations. Combining the optical data with Galaxy Evolution Explorer (GALEX) UV photometry, we find that all positive gradient galaxies show blue UV-optical colors. They also exhibit a tendency of having a lower stellar velocity dispersion. Positive gradient galaxies tend to live in lower density regions than negative gradient galaxies and are likely to have a late-type companion galaxy. On the other hand, massive early-type galaxies show negative color gradients. A simplistic population analysis shows that these positive color gradients are visible only for half a billion years after a star burst. Although the effective radius decreases and mean surface brightness increases due to this centrally concentrated star formation, the positions of the positive gradient galaxies on the fundamental plane cannot be reproduced by any amount of recent star formation. Instead it required a lower velocity dispersion.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.329-335
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• 2010

We investigate the sources of the variation of the high-latitude thermospheric neutral mass density depending on the interplanetary magnetic field (IMF) conditions. For this purpose, we have carried out the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM) simulations for various IMF conditions under summer condition in the southern hemisphere. The NCAR-TIEGCM is combined with a new empirical model that provides a forcing to the thermosphere in high latitudes. The difference of the high-latitude thermospheric neutral mass density (subtraction of the values for zero IMF condition from the values for non-zero IMF conditions) shows a dependence on the IMF condition: For negative $B_y$ condition, there are significantly enhanced difference densities in the dusk sector and around midnight. Under the positive-$B_y$ condition, there is a decrease in the early morning hours including the dawn side poleward of $-70^{\circ}$. For negative $B_z$, the difference of the thermospheric densities shows a strong enhancement in the cusp region and around midnight, but decreases in the dawn sector. In the dusk sector, those values are relatively larger than those in the dawn sector. The density difference under positive-$B_z$ condition shows decreases generally. The density difference is more significant under negative-$B_z$ condition than under positive-$B_z$ condition. The dependence of the density difference on the IMF conditions in high latitudes, especially, in the dawn and dusk sectors can be explained by the effect of thermospheric winds that are associated with the ionospheric convection and vary following the direction of the IMF. In auroral and cusp regions, heating of thermosphere by ionospheric currents and/or auroral particle precipitation can be also the source of the dependence of the density difference on the IMF conditions.