• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.1-5
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• 2009

In this study, we performed growth of InGaN/GaN multi quantum well (MQW) structures on semi-polar (1-10]) GaN facet on 8-degree off oriented stripe patterned (100) Si substratcs by MOVPE. The structural and optical properties of the InGaN/GaN multi quantum well (MQW) structures grown on (1-101) GaN stripe depend on $NH_3$ flow rate, TMI flow rate and growth temperature are characterized by cathodoluminescence (CL) and scanning electron microscopy (SEM). With the decrease of $NH_3$ flow rate, the threading dislocation of (1-101) GaN is considerably reduced. We could control the transition wavelength of InGaN/GaN MQW structures from 391.5 nm to 541.2 nm depend on the growth conditions.

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.139-150
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• 1998

We measured the terrestrial nightglow of OI $6300{\AA}$ in the thermosphere (~250km) using a ground-based Fabry-Perot interferometer at the King Sejong Station, Antarcticfrom March through September, 1997. The King Sejong Station is located at high latitude geographically ($62.22^{\circ}S,\;301.25^{\circ}E$) but at mid latitude geomagnetically ($50.62^{\circ}S,\;7.51^{\circ}E$). It is therefore the strategic location to measure the temperatures of the thermosphere in the Southern Hemisphere associated with both solar and geomagnetic activities. In this study, we analyzed the observed temperatures inrelation to F10.7 and Kp indices to examine the effect of the solar and the geomagneticactivities on high-latitude neutral thermosphere. During the observing period, the solaractivity was at its minimum. The measured temperatures are usually in the range between about 600~1000 K with some seasonal variation and are higher than those predicted by semi-empirical model, VSH (Vector Spherical Harmonics) and empirical model, MSIS (Mass-Spectrometer-Incoherent-Scatter)-86.

• Journal of computational fluids engineering
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• v.10 no.2
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• pp.7-14
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• 2005

In this study, the shallow water equations on the sphere is simulated by the proposed method which has high spatial resolution and is based on the CIP(Cubic Interpolated Pseudoparticle) method. The governing equations are approximated on the longitude-latitudinal coordinate system. To avoid the problems resulting from the convergence of the meridians toward high-latitude and singularities on the poles, the semi-Lagrangian and finite volume method are employed. in addition, the CIP method is employed to solve the advection equations and is extended to apply on the equations in the polar coordinate system. The mathematical formulation and numerical results are also described. To verify of the efficiency, accuracy and capability of proposed algorithm, the standard test cases proposed bv Williamson et. al are simulated and the results are compared with other results. As a result, it is found that the present scheme gives a good properties in preserving shapes of solution and settles the pole problems in solving the shallow water equations on the sphere.

• Ocean and Polar Research
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• v.39 no.3
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• pp.169-179
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• 2017

The "GeoDrifter" is a newly-developed surface drifter with high temporal resolution. It is the first time that high-frequency drifters have been deployed in the East/Japan Sea. The purpose of this study is to introduce the phenomena experienced by these drifters flowing along with the Tsushima Current across the East/Japan Sea, focusing on high-frequency variability, and to discuss them in comparison with previous observations. The observed basin-scale circulation of the Tsushima Current generally coincides well with the known schematic circulation. The GeoDrifter trajectories also show inertial oscillations almost everywhere in the oceanic regions of the East/Japan Sea, strong semi-diurnal tidal currents in the western part of Korea Strait, diurnal currents much stronger than semi-diurnal currents in the upstream region of the Nearshore Branch off the Japanese coast, and many warm eddies in the Yamato Basin, all comparable to the observational results reported in the previous studies. An interesting point is that the semi-diurnal tidal currents undergo a great spatial variation in the western part of the Korea Strait. The observed features that cannot be explained are, among others, strong counter-clockwise motions with oscillating period about 51 hours appearing in the upstream region of the Nearshore Branch off the Japanese coast and the different tidal behaviors between upstream and downstream regions of the latter.

• The Pure and Applied Mathematics
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• v.5 no.2
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• pp.109-114
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• 1998

Let H be a separable complex H be a space and let (equation omitted)(H) be the *-algebra of all bounded linear operators on H. An operator T in (equation omitted)(H) is said to be p-hyponormal if ($T^{\ast}T)^p - (TT^{\ast})^{p}\geq$ 0 for 0 ＜ p ＜ 1. If p = 1, T is hyponormal and if p = $\frac{1}{2}$, T is semi-hyponormal. In this paper, by using a technique introduced by S. K. Berberian, we show that the approximate point spectrum $\sigma_{\alpha p}(T) of a pure p-hyponormal operator T is empty, and obtains the compact perturbation of T.

• Macromolecular Research
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• v.16 no.3
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• pp.194-199
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• 2008

Four novel polyurethanes were prepared from 4-{(4-hydroxyphenyl)iminomethyl} phenol by reactions with two aromatic diisocyanates, 4,4'-diphenylmethane diisocyanate and toluene 2,4-diisocyanate, and two aliphatic diisocyanates, isophorone diisocyanate and hexamethylene diisocyanate. The polyurethanes formed were characterized by UV-vis, fluorescence, FT-IR, $^1H$-NMR, $^{13}C$-NMR, differential scanning calorimetry, thermogravimetry, and X-ray diffraction. The polymers were semi-crystalline and all polymers were soluble in polar aprotic solvents.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.167-171
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• 2021

The core-shell InGaN/GaN Multi Quantum Well-Nanowires (MQW-NWs) that were selectively grown on oxide templates with perfectly circular hole patterns were highly crystalline and were shaped as high-aspect-ratio pyramids with semi-polar facets, indicating hexagonal symmetry. The formation of the InGaN active layer was characterized at its various locations for two types of the substrates, one containing defect-free MQW-NWs with GQDs and the other containing MQW-NWs with defects by using HRTEM. The TEM of the defect-free NW showed a typical diode behavior, much larger than that of the NW with defects, resulting in stronger EL from the former device, which holds promise for the realization of high-performance nonpolar core-shell InGaN/GaN MQW-NW substrates. These results suggest that well-defined nonpolar InGaN/GaN MQW-NWs can be utilized for the realization of high-performance LEDs.

• Mass Spectrometry Letters
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• v.14 no.3
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• pp.79-90
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• 2023

Natural goods, especially therapeutic plants, are abundant in the World. Because they have the ability to provide all humanity with countless advantages as a source of medicines, medicinal plants are presently receiving more attention than ever. These plants' therapeutic efficacy is based on bioactive phytochemical components that have clear physiological effects on the human body. The drying process is crucial for the preparation of plant materials prior to extraction since freshly harvested plant materials include active enzymes that create active components, intermediates, and metabolic processes. Many of the phytoconstituents may be extracted using the semi-polar solvent methanol. The goal of the current work is to use the GC-MS gas chromatography- mass spectrometry technology to identify the phytochemicals and review their biological activity. In methanol leaf extract, 5 phytocompounds were found in Ricinus communis, 5 phytocompounds in Pongamia pinnata, 12 phytocompounds in Datura metal, 7 phytocompounds in Azadirachta indica, 11 phytocompounds in Acalypha indica.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.95-111
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• 2012

Relationship between plankton assemblage and environmental factors in a semi-closed Chunsu Bay was examined. Temporal changes in phytoplankton assemblage was rather drastic than those found in most Korean coastal area in the Yellow Sea primarily due to the seawater temperature (T) and nutrient input from the dikes nearby. Freshwater discharge seemed to cause winter time increase of Diatoms (February) and summer time increase of Dinoflagellates at surface (July to August). Structural change in cell size with time was also found in Diatom. Zooplankton community structure was also changed with season probably due to the food concentration, seawater temperature and salinity (S). From principal component analysis (PCA) of zooplankton distribution, it was postulated that seasonal environmental changes such as T and S could explain about 32% of variability in zooplankton distribution along with phytoplankton cell numbers, while freshwater discharge could explain about 17%. Comparing with past data of 1985-1986, 1991-1992, the distributional patterns and percent composition of major species, Acartia hongi, Paracalanus parvus sensu lato and Centropages abdominalis, were similar. However, the abundances have been increased more than three times. The composition of other taxa than copepods showed significant changes.

• Journal of Astronomy and Space Sciences
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• v.22 no.3
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• pp.197-210
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• 2005

Results of 7 nights of CCD VR photometry of the intermediate polar 1RXS J062518.2+733433 obtained at the Korean 1.8m telescope are reported. The corrected ephemeris for the orbital minimum is BJD (Orb.min) = 2453023.6159(42)+0.1966431(33) (E-1735). The corrected ephemeris for the spin maximum is BJD (spin max) = 2452893 78477 (10)+0.01374116815 (17) (E-15382) (cycle numbering corresponds to that of Staude et al.2003). The variations of the shape of the individual spin variations are highly correlated in V and R. The phase of the spin maximum is found to be dependent on the orbital phase. The corresponding semi-amplitude of sinusoidal variations of phase is $0.11{\pm}0.03.$ This new phenomenon is explained by the changing viewing conditions of the accreting magnetic white dwarf, and should be checked in further observations this star and for other intermediate polars. To avoid influence of this effect on the analysis of the long-term spin period variations, the runs of at least one orbital period are recommended. Results of time series analysis are presented in tables.