• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.3
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• pp.365-370
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• 1995

This study was conducted to obtain the basic information on salinity tolerance in Italian Ryegrass. Seeds of 20 cultivars that contained diploid(9 cultivars) and tetraploid(l1 cultivars) types were exposed to eight levels of NaCl concentration ranging from 0 to 350 mM under three levels (15$^{\circ}C$, 2$0^{\circ}C$ and $25^{\circ}C$) of temperature. There were highly significant differences in germination percentage among the levels of NaCl concentration, levels of temperature and cultivars, respectively. Average germination percentage of cultivars in control(no NaCl was higher at 2$0^{\circ}C$(90.1%) than that of $25^{\circ}C$(87.8%) or 15$^{\circ}C$(87.5%). Average germination percentage of cultivars began to decrease over 200mM of NaCl concentration. The degree of decrease in germination was higher at $25^{\circ}C$ than that of 15$^{\circ}C$ or 2$0^{\circ}C$. At 2$0^{\circ}C$, the germination percentage and gemination speed were gradually decreased as NaCl concentration increased. The average germination day was lengthened by the increase of NaCl concentration and temperature. The germination percentage in diploid types were higher than that of tetraploid types but the average germination day in diploid types was shortened more than that of tetraploid types, regardless of temperature and NaCl concentration.

• Research in Mathematical Education
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• v.13 no.1
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• pp.49-61
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• 2009

In this paper some attempts have been made: (a) To identify all the elementary minor concepts of the Highest Common Factor (H.C.F.) and the Lowest Common Multiple (L.C.M.), and (b) To find the sequential order of these elementary concepts. Total 385 elementary minor concepts have been identified and sequenced.

• Journal of the Korean Mathematical Society
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• v.40 no.3
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• pp.563-575
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• 2003

We show that if a connected Stein manifold M of dimension n has the holomorphic automorphism group Aut(M) isomorphic to $Aut(C^k {\times}(C^*)^{n - k})$ as topological groups, then M itself is biholomorphically equivalent to C^k{\times}(C^*)^{n - k}$. Besides, a new approach to the study of U(n)-actions on complex manifolds of dimension n is given.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.261-267
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• 1988

$\beta$-Sialon powder was prepared by the reduction-nitridation reaction from the mixture of Wando Pyrophyllite and carbon black at 135$0^{\circ}C$ in $N_2$ atmosphere. $\beta$-SiC powder was added to the prepared $\beta$-Sialon powder to make $\beta$-Sialon-SiC composite. The $\beta$-Sialon-SiC composites were sintered pressurelessly at 175$0^{\circ}C$ for 2h, using $Y_2O_3$ and $ZrO_2$(monoclinic) as sintering aids. Comparatively higher values of the fracture toughness (3.8 MN/㎥/2), M.O.R. (470 MN/$m^2$) and vickers microhardness (13.7 MN/$m^2$) were obtained when 10 wt% $Y_2O_3$ was added as a sintering aid. The improved fracture toughness and M.O.R. are assumed to be the results of crack deflection and crack branching by the second phase SiC particles.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.2
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• pp.103-115
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• 1981

The cathodic reactions of lead anodic films formed in phosphoric acid, oxalic acid and sodium hydroxide solutions and the reactivities of Di-iso-butylnitrosoamine (DBNA) in sea water at $15\sim30^{\circ}C$ were studied by means of constant current-potential method. Besides, various contants and thermodynamic quantities obtained in the experiment were also do-scribed to explain the reactivities of protons that entered in the anodic film by being transferred across the metal-oxide interface. The electrode reactions of lead anodic film formed in sodium hydroxide solution in 60mM DBNA+0.5M NaCl did not occur because of complete insulator formed on anodic film. The values of $(\partial\triangle E_{H^+}/\partial T)_{i=const}$, estimated with Bead anodic films formed in phosphoric acid in 60mM DBNA+0.5M NaCl and 60mM $DBNA+6\%_{\circ}$ sea water were $-0.006\;V/^{\circ}C\;and\;-0.005\;V/^{\circ}C$, thus being nearly coincided, but the values of $(\partial E_o/\partial T)_{i=o}$ were $0.002\;V/^{\circ}C\;and\;-0.002\;V/^{\circ}C$, being completely inversed.

• The Korean Journal of Malacology
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• v.18 no.2
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• pp.77-82
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• 2002

This study was performed to find out the optimal kind of additive and concentration of ethylene glycol (EG) as the cryoprotectant on the D-shaped larvae of arkshell, Scapharca broughtonii. The larvae in straws was carried in the programed freezer set uo at 0$^{\circ}C$, frozen to -12$^{\circ}C$ by the freezing rate of -1$^{\circ}C$/min, held for 10 minutes, seeded at -12$^{\circ}C$, finally refrozen to -35$^{\circ}C$ by the freezing rate of -1$^{\circ}C$/min and then directly plunged into liquid nitrogen. The survival of larvae frozen in 1.0 M and 2.0 M ethylene glycol added with 0.5 M sucrose were high (50.5 ${\pm}$ 1.3% and 51.9 ${\pm}$ 1.7%, respectively) in the early D-shaped larvae cryopreserved in 1 M and 2 M ethylene glycol diluted with 0.2 M and 0.5 M fructose, glucose and sucrose. In the late D-shaped larvae were cryopreserved according to five concentrations of ethylene glycol added with 0.5 M sucrose, the survival of larvae frozen in 2.0 M ethylene glycol was the highest as 51.9 ${\pm}$ 1.7%. The morphological differences in cells between unfrozen and frozen-thawed D-shaped larvae were not found by the scanning and transmission electron microscopy.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.185-190
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• 2008

Nine wells have been developed for uses of thermal waters at the Icheon hot spa area. Drilling depths of those hot spring wells range from 166 to 294 m and their piezometric heads are located at about 50 m below the surface. Using the differences between the surface and bottom temperatures within all boreholes, we can simply estimate geothermal gradient in this area. Thus, we obtained the highest, lowest and average gradient values as $64^{\circ}C/km$ from SB-2 well, $45^{\circ}C/km$ from SB-1 well and approximately $54.28^{\circ}C/km$, respectively. However, observing the MRD-2 well additionally drilled into the depth of 996 m, we found out that this study area has widely experienced the temperature disturbance due to thermal groundwater penetration through the fracture systems within the depth of 720 m. Unlikely this phenomenon, we can conclude that the groundwater flow below the depth of 720 m does not exist. Therefore, using only those temperature data below the 720 m depth, we can estimate reasonable geo-thermal gradient values as $33^{\circ}C/km$ in this study area. Pumping test shows that outflowing temperature is $36^{\circ}C$ corresponding to the temperature logging data at 720 m depth.

• Journal of Aquaculture
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• v.10 no.2
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• pp.219-225
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• 1997

The growth and size variation of rotifer (Brachionus plicatils) were examined at the various water temepratures ranging form 18 to $36^{\circ}C$, and under continuous light condition. Either Chlorella ellipsoidea or $\omega$-yeast were fed to rotifer as a food organism. Compared to large-type rotifer fed of $\omega$-yeast, those fed on C. ellipsoildea generally showed higher growth at 7th after starting culture under the water temperaure of less than $30^{\circ}C$. Above such temperature, the large-type rotifer fed on $\omega$-yeast showed higher growth rather than those fed on C. ellipsoidea and the maximum cell number reached 1,420 ind./m$\ell$ at $36^{\circ}C$, whereas when the small-type rotifer was fed on $\omega$-teast, its maximum cell number was to be 1,669 ind./m$\ell$at $34^{\circ}C$. The striking decrease in size was found in large-type rotifer which was to be $112.1\mu m$m(initial : 202.0${\mu}{\textrm}{m}$) when they were fed on C. ellipsoidea at $34^{\circ}C$ for 5 days after starting culture. A great increase in size from the initial of 157.0 to $201.3\mu m$mwas show in small-type rotifer fed on $\omega$-yeast at $20^{\circ}C$,for 5 days. The present results demonstrated that size variation of rotifer could be controlled by changing culture temperature.

• The Journal of Natural Sciences
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• v.8 no.2
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• pp.137-146
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• 1996

To increase the oxidation-resistance of graphite substrate, we have tried to form SiC film on its surface by Sol-Gel method. TEOS(Tetraethyl orthosilicate) and phenol resin have been used as silicon(Si) and carbon(C) sources, respectively. In order to know the effect of the TEOS Sol concentration on the forming of SiC film, we have taken 5 different $H_2O$/TEOS mol ratios of 2, 4, 6, 8 and 10. And the coating states of SiC on the graphite substrate have been analyzed with X-ray diffractometer and scanning electron microscope (SEM), and we have obtained about 5${\mu}m$, 12${\mu}m$, 7${\mu}m$, 7${\mu}m$ and 2 ${\mu}m$ as the thickness of SiC coating layers, respectively. For also knowing the oxidation resistance the SiC coated graphites at $1600^{\circ}C$ were heated again at $1000^{\circ}C$ under air atmosphere for 1 hr, and as a result we have received the weight losses of 26.17%, 20.97%, 17.28%, 21.73% and 28.13%, respectively.

• Journal of Sensor Science and Technology
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• v.16 no.3
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• pp.197-201
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• 2007

The magnetron reactive ion etching (RIE) characteristics of polycrystalline (poly) 3C-SiC grown on $SiO_{2}$/Si substrate by APCVD were investigated. Poly 3C-SiC was etched by $CHF_{3}$ gas, which can form a polymer as a function of side wall protective layers, with additive $O_{2}$ and Ar gases. Especially, it was performed in magnetron RIE, which can etch SiC at a lower ion energy than a commercial RIE system. Stable etching was achieved at 70 W and the poly 3C-SiC was undamaged. The etch rate could be controlled from $20\;{\AA}/min$ to $400\;{\AA}/min$ by the manipulation of gas flow rates, chamber pressure, RF power, and electrode gap. The best vertical structure was improved by the addition of 40 % $O_{2}$ and 16 % Ar with the $CHF_{3}$ reactive gas. Therefore, poly 3C-SiC etched by magnetron RIE can expect to be applied to M/NEMS applications.