• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.2
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• pp.121-128
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• 1996

The optimum conditons were experimentally established for the powder synthesis and sintering of the feed-rods for $LiNbO_3$ crystal growth by a floating zone method. At the lower synthesis temperatures(700, $ 800^{\circ}C$) the minor amounts of $Li_2CO_3$ and $Nb_2O_5$ were present in the synthesized $LiNbO_3$ powder and at the higher temperature the particle size increased which is not favorable for the sintering process for the feed-rods. $LiNbO_3$ powder synthesized at $950^{\circ}C$ for 12 hours was found to be the best because it contains only the$LiNbO_3$ phase with the small particle size and uniform particle size distribution. As the sintering temperature and the soaking time increase, the sintered feed-rods exhibited the higher sintered density and grain growth phenomena. The $LiNbO_3$ feed rods sintering at $1100^{\circ}C$ for 2 hours were found to have the best microstructure for the precursor feed-rods of the floating zone crystal growth because of their higher density, small grain size and uniform particle size distribution. As the sintering temperature and the soaking time increase, the sintered feed-rods exhibited the higher sintered density and grain growth phenomena. The $LiNbO_3$ feed rods sintering at $1100^{\circ}C$ for 2 hours were found to have the best microstructure for the precursor feed-rods of the floating zone crystal growth because of their density, small grain size and uniform grain size distribution.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.526-534
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• 2019

The average coastline and the erosion control line introduced as the management coastline, and the average shoreline (MSL) was established from the observed coastline. Also, the median grain size and the wave height of 30-years return period were applied. The erosion control line (ECL) was established through the model, HaeSaBeeN. These two lines set the coastline for evaluation. Based on the observed monitoring data along the coastline, the 1-day variation according to the normal distribution was used to estimate the regional variation, and the width of the erosion was calculated by applying the median grain size (D₅₀) and the wave height of 30-years return period through the high-wave coastal erosion width model, i.e., HaeSaBeeN.

• Journal of The Geomorphological Association of Korea
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• v.26 no.1
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• pp.15-26
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• 2019

In this study, we investigated the grain size, lithological type, and shape of coarse bed materials in the upper and middle reaches of Gongneungcheon River. For this purpose, 11 sampling points were selected along the river. For 100 samples of the coarse bed materials at each point, three axes (long, intermediate, and short) of samples were measured, and their lithological types were also identified. By measuring grain size, the sphericity and flatness of samples were calculated. Finally, every particle was classified into four shape categories: sphere, disc, blade and rod. We found that the grain size in incised meandering reach is the largest. This is mainly due to the supply of coarse materials from steep valley sides along the meandering channel. According to the lithological analysis, all samples were identified as granite, gneiss and schist, and quartz. The proportion of granite decreased, whereas the proportion of gneiss and schist increased downstream. These patterns indicate that the bedrock distribution within the study area accounts for the downstream lithological variation of coarse bed materials. With regard to the grain shape, sphericity gradually decreased while flatness gradually increased downstream. In the case of the shape classification, unlike the general downstream pattern of grain shape, the proportion of the sphere type decreased and the proportion of the blade type increased downstream. Such a reversal change in the downstream direction turns out to be determined by the lithology (such as foliation, bedding and the pattern of weathering) of coarse bed materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.441-447
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• 2003

When a SnO$_2$ thin film was deposited by thermal CVD, two different types of growth behavior that were dependent on the deposition temperature were observed. The film grown at 475$^{\circ}C$ had a wide grain size distribution and a faceted surface shape. On the other hand, the film grown at 5$25^{\circ}C$ had a relatively narrow grain size distribution and a rounded sulfate shape. The aspects of grain shape and growth behavior agree well with the theory of gram growth and a roughening transition. The charge tarrier density decreased with deposition time. According to photoluminescence measurements, the peak intensity of the spectra occurred at approximately 2.5 eV, which is related to oxygen vacancies, and decreased with increasing of deposition time. These measurement results suggest that the number of oxygen vacancies, which is related to the electrical conductivity, decrease with deposition time.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.2
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• pp.135-144
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• 2021

End-member (EM) analysis of grain-size distribution data for detrital fractions of IODP Site U1430 core sediments from the South Korea Plateau (East Sea) identified 4 EMs grain-size populations (EM) which represent either Asian dusts (Hwangsa) or volcanic ashes. The two EMs representing volcanic ashes consist of fine and coarse glass shards with various morphologies and constitute 0-82% of the total grain-size distributions. The 33% mixing percentage of volcanic ash EMs seems appropriate for a cut-off value for discrimination of grain-size data influenced by volcanic ash input from those dominated by Hwangsa.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.593-600
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• 1988

The properties of 10 kinds of MgO clinker were investigated to know the effect of MgO clinker's porperties on corrosion of MgO-C brick. For MgO clinker, chemical composition, porosity, density, periclase grain size, and microstructure were examined, while slag corrosion resistance was examined for MgO-C brick. In MgO clinker pore size and it's distribution, periclase grain size, impurities composition and the composition of grain boundaries are more important factors to determine corrosion degree of MgO-C brick than density, potosity and MgO purity.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.614-617
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• 1995

Thin CoCrTa/Cr films were deposited on glass substrates at $280^{\circ}C$ with or without Al underlayer. The coercivity of CoCrTa increased considerably by introducing an Al underlayer. The grain size of Cr thin film deposited on Al underlayer became smaller than that of Cr thin film deposited on glass substrate. The grain size of CoCrTa thin film was determined by Cr grain size. The cause of the coercivity increase seems to be associated with the refinement and uniform distribution of CoCrTa grains.

• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.71-78
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• 2009

The precipitation behavior of solute carbon and nitrogen strongly affects the mechanical properties of low-carbon automotive panel. In the present study, the effects of aluminum and solute nitrogen on the bake hardenability and strain aging of extremely low-carbon steel with carbon content below 15 ppm has been investigated. The ferrite grain size and distribution of precipitates were varied with the amount of aluminum content of 0.003 to ~ 0.100 wt% in a constant solute carbon and nitrogen. With increasing the aluminum content, the ferrite grain size is increased and strain aging is delayed. The strain aging is also delayed by increasing the annealing temperature, although the ferrite grain size is not much changed.

• Journal of the Korean Geographical Society
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• v.32 no.4
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• pp.435-444
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• 1997

Bars in a river bed show the flow of the river, the shape of a river bar can be easily measured in any river. The purpose of this study is to research the morphological characteristics of river bars. The case study area is the lower Golgi River, six bars were examined. All six bars are gravel bars with a grain size in excess of 2 millimeters. Four of the bars are longitudinal bars, in which the direction of the bar follows the river current. After analyzing the gravel in the bars, it was determined that as the gravel flows down the river, gravel grain size decreases while grain roundness increases. The shape of bar varies locally according to flow regime, channel slope, and w/d ratio.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.314-319
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• 2000

Microstructueral development and electrical properties in ZnO-Bi2O3-ZnAl2O4 system were investigated with ZnAl2O4 content(0.1~1.0 mol%). The shrinakge of specimens started around $700^{\circ}C$ and finished at 110$0^{\circ}C$, reaching a maximum shrinkage rate at 80$0^{\circ}C$. The shrinkage rate is strongly related to the fromation of a Bi-rich liquid. The increase of the ZnAl2O4 content inhibited the grain growth of ZnO. Most of ZnAl2O4 particles located at the grain boundaries were about 2~3${\mu}{\textrm}{m}$. ZnO grain size changed little up to 110$0^{\circ}C$, but increased markedly above 115$0^{\circ}C$, especially at lower ZnAl2O4 content. Drastic decreasing in breakdown voltage(Vb) with increasing temperature is expected to be dependent on the ZnO grain size and the distribution of the largest grains between the electrode. The nonlinear I-V characteristic was significantly influenced by the ZnAl2O4 content, which exhibited a maximum value at about 15${\mu}{\textrm}{m}$ of ZnO grain size.