• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.133-136
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• 2004

In-situ collection experiments were performed to analyze inflowing sedilnents behavior as a basic study of topographical change in Nakdong River Estuary. Sediment rate and bed load flux ranged from 0.0004 to $0.472\;g/cm^2/day\;and\;0.0005\~1.7579\;g/cm^2/day$, respectively. The settling velocity of suspended particulate matter was estimated in tire range of $0.339\~1.010\;cm/sec$, The grain size analysis shows that surface sediments in backside of sandbar and bed load in front of dike have a similar grain size distribution. It is considered that the source of surface sediments in backside of sandbar were flowed in from Nakdong River. In order to verify the characteristics of inflowing sediments behavior, detailed surveys around Nakdong River Estuary need to be carried out, continuously.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.169-172
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• 2002

Recently, the application of 3-roll mill is increasing, because of its flexibility in spread control and stand arrangements due to its compact size. But deformation characteristics and microstructural change in the process is not well known. In this study, austenite grain size (AGS) predictions were made by isothermal FE analyses and a microstructure model available in the literature. From this study, the effect of draught on the AGS characteristics was analyzed based on the divided zones of two major recrystallization behaviors.

• The Journal of Engineering Geology
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• v.27 no.2
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• pp.133-141
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• 2017

In this study, filter conditions by difference in grading between core material and filter material used for dam construction was applied as evaluation condition for surrounding ground conditions near excavation site in a bid to identify the risk of land subsidence resulting from the erosion of soil particles. To that end, filter conditions proposed for the test was evaluated and the risk of land subsidence depending on grain size conditions was also evaluated using the filter conditions developed by COE. Consequently, evaluation diagram that can be used to determine the risk of land subsidence using grain size conditions obtained from ground investigation data was developed, which is expected to help evaluate the possibility of land subsidence depending on changes to the stratum. To simulate the particle flow process, PFC3D program was used. It's not only intended to determine the land subsidence pattern caused by falling ground water level but also predict and evaluate the land subsidence caused by soil erosion using grain size condition which can be verified by numerical analysis approach.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.556-562
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• 2011

We carried out this study to evaluate the grain refining in and the mechanical properties of alloys that undergo severe plastic deformation (SPD). Conventional rolling (CR) and cross-roll rolling (CRR) as SPD methods were used with Ni-20Cr alloy as the experimental material. The materials were cold rolled to a thickness reduction of 90% and subsequently annealed at $700^{\circ}C$ for 30 min to obtain a fully recrystallized microstructure. For the annealed materials after the cold rolling, electron back-scattered diffraction (EBSD) analysis was carried out to investigate the grain boundary characteristic distributions (GBCDs). The CRR process was more effective when used to develop the grain refinement relative to the CR process; as a result, the grain size was refined from $70{\mu}m$ in the initial material to $4.2{\mu}m$ (CR) and $2.4{\mu}m$ (CRR). These grain refinements have a direct effect on improving the mechanical properties; in this case, the microhardness, yield and tensile strength showed significant increases compared to the initial material. In particular, the CRR-processed material showed more effective values relative to the CR-processed materials. The different texture distributions in the CR (001//ND) and CRR (111//ND) were likely the cause of the increase in the mechanical properties. These findings suggest that CRR can result in materials with a smaller grain size, improved texture development and improved mechanical properties after recrystallization by a subsequent annealing process.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.203-212
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• 2011

The objective of this paper is to identify the present-day surficial sediment distribution patterns of the tidal river, Gongneungcheon, through the grain size and statistical analysis. Four major findings of this study are as follows; First, the composition of sediments over the study area are mainly silt in texture. Second, the surficial sediment distribution reveals that grain size becomes coarser as they approach seawards not only in summer but also in winter. It can be concluded that tidal flows play a significant role, especially in winter, in the distribution of surficial sediments in Gongneungcheon. However, samples obtained in summer were relatively small in mean size and showed better sorting compared to those obtained in winter. Third, the mean sizes of the samples on the transects decrease as the distance from the channel increases. Finally, the artificial structure such as a floodgate affects the distribution of the sediments.

• Korean Journal of Materials Research
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• v.32 no.4
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• pp.181-185
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• 2022

In this study, phase-pure titanium dioxide TiO₂ ceramics are sintered using standard high-temperature solid-state reaction technique at different temperatures (1,000, 1,100, 1,200, 1,300, 1,400 ℃). The effect of sintering temperature on the densification and impedance properties of TiO₂ ceramics is investigated. The bulk density and average grain size increase with the increase of sintering temperature. Impedance spectroscopy analysis (complex impedance Z^* and complex modulus M^*), performed in a broad frequency range from 100 Hz to 10 MHz, indicates that the TiO₂ ceramics are dielectrically heterogeneous, consisting of grains and grain boundaries. The complex impedance Z^* -plane indicates the resistance of grains of the TiO₂ ceramics increases with increasing sintering temperature, while that of grain boundaries develops in the opposing direction. The complex modulus M^*-plane shows a grain capacitance that seems to be independent of the sintering temperature, while that of the grain boundaries decreases with increasing sintering temperature. These results suggest that different sintering temperatures have effects on the microstructure, leading to changes in the impedance properties of TiO₂ ceramics.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.303-313
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• 2020

Rice grain shape is one of the key components of grain yield and market value. An understanding of the genetic basis of the variation in grain shape could be used to improve grain shape. In this study, we developed a total of 265 F₂ individuals derived from a cross between japonica cultivars (Josaeng-jado and Langi) and used this population for quantitative trait locus (QLT) analysis. Correlation analysis was performed to identify relationships between grain traits (GL: grain length, GW: grain width, L/W: ratio of length to width, TGW: 1,000 grain weight). The grain shape was positively correlated with GL and TGW, and negatively correlated with GW. In QTL analysis associated with grain shape, one QTL for GL, qGL5, detected on chromosome 5, explained 20.3% of the phenotypic variation (PV), while two QTLs, qGW5 (PV=36.1) and qGW7 (PV=26.1), for GW were identified on chromosomes 5 and 7, respectively. Evaluation of the effects of each of the QTLs on the grain shape in the population showed a significant difference in the grain size in positive lines compared with the lines without the QTLs. According to the QTL combination of the allelic-types, the grain shape of the tested lines varied from semi-round type to long spindle-shaped type. The results of this study extend our knowledge about the genetic pool governing the diversity of grain shape in japonica cultivars and could be used to improve the grain shape of this species through marker-assisted selective breeding in Korea.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1087-1090
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• 2009

A unique process was developed to improve the mechanical properties of a circular tube. In this proposed process, a large amount of strain is applied to the wall of tube, leading to grain refinement in the material. In order to investigate characteristics of microstructural evolution such as the distribution of grain size and misorientation angle during the process, an EBSD OIM analysis was carried out. The analysis confirms that the proposed process can very effectively produce a circular tube with ultrafine-grains.

• Plant Resources
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• v.3 no.3
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• pp.206-210
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• 2000

A total of 20 soybean recommended varieties which were developed until late 1980's in Korea was evaluated at Suwon. Comprehensive evaluation and correlation analysis were conducted on the agronomic characters. Great variations were found in these genotypes for branch number, pod number, and grain yield per plant. The variation in number of pods/plant ranged from 53 to 164, and in grain yield from 25.9 to 68.8 g. The coefficient of variation for most of the characters had a wide range. In correlation coefficient, grain yield per plant showed a positive phenotypic association with weight of pods, pod number of branches, and weight of stem. Multiple regression analysis was done to formulate selection criteria. It indicated that stout and medium-stature genotypes with more branches, resulting in varieties with more pods per plant but with medium-size seeds are available to obtain high-yielding varieties.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.362-363
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• 2006

Nano-structured tungsten carbide compacts with cobalt matrices (WC-Co) offer new opportunities for achieving superior hardness and toughness combinations. A unified modeling and simulation tool has been developed to produce maps of sintering pathways from nanocrystalline WC powder to sintered nano-structured WC-Co compacts. This tool includes (1) die compaction, (2) grain growth, (3) densification, (4) sensitivity analysis, and (5) optimization. All material parameters were obtained by curve fitting based on results with two WC-Co powders. Critical processing parameters are determined based on sensitivity analysis and are optimized to minimize grain size with high density.