• Bulletin of the Korean Chemical Society
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• v.25 no.1
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• pp.51-54
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• 2004

Gallium nitride (GaN) powders were prepared by calcining a gallium(III) nitrate salt in flowing ammonia in the temperature ranging from 500 to 1050 $^{\circ}C$. The process of conversion of the salt to GaN was monitored by X-ray diffraction and $^{71}Ga$ MAS (magic-angle spinning) NMR spectroscopy. The salt decomposed to ${\gamma}-Ga_2O_3$ and then converted to GaN without ${\gamma}-{\beta}Ga_2O_3$ phase transition. It is most likely that the conversion of ${\gamma}-Ga_2O_3$ to GaN does not proceed through $Ga_2O$ but stepwise via amorphous gallium oxynitride ($GaO_xN_y$) as intermediates. The GaN nanowires and microcrystals were obtained by calcining the pellet containing a mixture of ${\gamma}-Ga_2O_3$ and carbon in flowing ammonia at 900 $^{\circ}C$ for 15 h. The growth of the nanowire might be explained by the vapor-solid (VS) mechanism in a confined reactor. Room-temperature photoluminescence spectra of as-synthesized GaN powders obtained showed the emission peak at 363 nm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.3
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• pp.79-86
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• 2013

In order to analyze the electrical performance of ZnO surge arresters stressed by the combined DC and AC voltages that are generated in DC/AC converter systems, the leakage current properties of ZnO surge arrester blocks deteriorated by impulse currents were investigated. The test specimens were deteriorated by the 8/$20{\mu}s$ impulse current of 2.5kA and the leakage currents flowing into the deteriorated zinc oxide(ZnO) arrester blocks subjected to the combined DC and power frequency AC voltages are measured. As a result, the leakage currents flowing through deteriorated ZnO surge arrester blocks were higher than those flowing through the fine ZnO surge arrester blocks and the larger the injection number of 8/$20{\mu}s$ impulse current of 2.5kA is, the greater the leakage current is. The leakage current-voltage curves(I-V curves) of the fine and deteriorated ZnO surge arrester blocks stressed by the combined DC and AC voltages show significant difference in the low conduction region. Also the cross-over phenomenon is observed at the voltage close to the knee of conduction on plots of I-V curves.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.411-416
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• 2010

Interest in application of ultraviolet light technology for primary disinfection of potable water in drinking water treatment plants has increased significantly in recent years. The efficacy of disinfection processes in water purification systems is governed by several key factors, including reactor hydraulics, disinfectant chemistry, and microbial inactivation kinetics. The objective of this work was to develop a computational fluid dynamics(CFD) model to predict velocity fields, mass transport, chlorine decay, and microbial inactivation in a continuous flow reactor. In this paper, It describe the how to design optimal UV disinfection device for ground water, BWT and rainwater. Spring shape instrument silver coated located in inner side of disinfection chamber. It make lead the active flowing movement target water and maximize disinfection performance. To search the optimal design method, it was performed computer simulation with 3D-CFD discrete ordinates model and manufactured prototype. Using proposed design method, performed simulation and proved satisfied performance.

• Journal of the Korean Society of Clothing and Textiles
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• v.47 no.2
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• pp.244-255
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• 2023

Patterns abstractly depicting flowing water with Chinese characters such as gong, wan(man), or wang continued endlessly and curved water patterns began appearing on textiles during the Song Dynasty. Though Song curved water patterns encompassed poetic sentiments such as "falling flowers and flowing water," the meaning faded with time, and these patterns were depicted in backgrounds with flowers added to brocade (Geum-sang-cheom-hwa). During the Ming and Qing Dynasties, combinations of diverse patterns, including flowers, butterflies, dragons, and auspicious treasures became fashionable, rather than the gong- and wan-shaped curved water patterns. Likewise, during the Joseon Dynasty, curved water patterns were preferred as background rather than as primary patterns. They were overlaid with flowers and clouds. The overlaid flower patterns included four-season flower patterns (17th-18th centuries), round flower patterns (19th century), and large flower patterns (20th century), which were identical to flower patterns fashionable at the time and arranged at intervals on complex curved water pattern backgrounds. In contrast, simple Ruyi types were more numerous than the four-Ruyi types fashionable at the time with regard to cloud patterns. Added here were Taiji (great ultimate symbol) or crane patterns, thus seeking to depict diverse auspicious Ruyi such as wish fulfillment and longevity.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.369-372
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• 2008

In this research experimentally analyzes the flow characteristics of a combined High flowing Self-Compacting Concrete of which the viscosity agent and defoaming agent addition amount are changed, to make the combined High flowing Self-Compacting Concrete that can secure the required flow performance and air amount. As a result of the experiment, the slump flow of the combined High flowing Self-Compacting Concrete added with viscosity agent increases when the viscosity agent addition amount is 0.2%(${\times}$W %). When viscosity agent addition amount increases, viscosity agent shows that it largely deviates from the regulation value in the flow time of V-funnel, which is presented in the JSCE standards (grade 2). Also, all mixtures, except for mixtures added with viscosity agent, defoaming agent, and AE agent, do not meet a target air amount $4.5{\pm}1.5%$. High flowing Self-Compacting Concrete mixtureadded with defoaming agent shows that although time passes after its first mixture, its air amount reduces a little. Based on the experiment, we can know an optimal polymer amount to obtain the required flow performance

• Korean Journal of Ichthyology
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• v.20 no.3
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• pp.179-189
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• 2008

Standard length (SL) and gonadosomatic index (GSI) of Plecoglossus altivelis were investigated from March to October 2007 in Seomjin River and streams flowing to the East Sea, Korea. Water temperatures were $17{\sim}23^{\circ}C$ during the spawning season, which ran from late September to early November in Seomjin River and early August to mid-October in streams flowing to the East Sea. The GSI and HSI variations of ayu population in Seomjin River increased earlier than in populations in streams flowing to the East Sea with similar variation in water temperature. Histological study of ovaries showed that the start of spawning of P. altivelis in Seomjin River was later than in streams flowing to the East Sea. Overall, fecundity increased with increase in SL and not by site specificity. The SL of P. altivelis increased as the river scale increased. Mean length of specimens from Seomjin River (river length: 223.86 km, river area: $4,911.89km^2$) was $194{\pm}15.3mm$, from Osip Stream (55.76 km, $393.78km^2$) $185{\pm}15.5mm$, from Yangyang Namdae Stream (54 km, $474.08km^2$) $142{\pm}11.8mm$, and from Joosoo Stream (21.1 km, $141.47km^2$) $136{\pm}16.7 mm$.

• Korean Architects
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• s.571
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• pp.16-17
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• 2016

• 레미콘
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• no.6 s.12
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• pp.2-10
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• 1987

• Proceedings of the Korean Magnestics Society Conference
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• 1992.03a
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• pp.42-43
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• 1992

• Magazine of the Korea Concrete Institute
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• v.13 no.3
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• pp.26-31
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• 2001