• Journal of Korea Water Resources Association
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• v.39 no.11 s.172
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• pp.961-968
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• 2006

Since a small harbor is often located near surf zone areas which have great influences of sediment transport, there is a great possibility that the sediment will be deposited inside of the harbor. The sediment transport occurring around the harbor entrance can't be explained by the wind wave and wave induced current. In this study, it was investigated the mechanism of the entrainment of sediment into a small harbor with permeable breakwater using hydraulic experiments in 3D wave basin. It is found out that the significant sediment entrainment produced when the mode of oscillation in the harbor became the 1st mode. In the case where the incident wave period was shorter than the period that caused higher mode oscillation in harbor, only a little amount of sediment entrainment took place. The vortex shedding from the top of secondary breakwater played very important roll in the entrainment of sediment into the harbor. It is also found that the small jetty attached at the top of secondary breakwater could effectively prevent the entrainment of sediment into the harbor.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.291-301
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• 1998

The objective of this study is to analyze the characteristics of flow and bed topography with changing bed material in a 180-degree, with constant-radius curved experimental channel. Sand($D_{50}$ = 0.56 mm, s = 2.65) and anthracite($D_{50}$ = 0.26 mm, s = 1.54) were selected as bed materials. The maximum scour depth was found to be about two times for the mean flow depth at the outer bank of bend angle $30^{\circ}~60^{\circ}$, and in case of anthracite, it was found upper part of bend angle $5^{\circ}~15^{\circ}$ than that of sand. Regardless of bed materials the path of maximum streamwise velocity is skewed inwards in the upper part of the bend, the maximum velocity shifts outwards, and it lagged downward as bed roughness increases. The maximum skewed angle of flow grows faster in the smooth bottom than in the rough one, and its value also increases. The secondary flow in anthracite bottom was measured larger than that of sand one, and two cells of secondary flow was found in this experiment.

• Resources Recycling
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• v.28 no.4
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• pp.3-14
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• 2019

Lead is one of the common non-ferrous metals used in modern industry. The usage of lead continues to increase and has risen from 5 million tonnes per year worldwide in the 1970s to 11 million tonnes in the 2010s. In principle lead is virtually 100 % recyclable as an element without loss of quality. The recycling of lead scrap reduces the energy consumption and environmental burden, comparing to the primary metal production. Therefore production of secondary lead from scrap has been steadily growing and at present it meets approximately 60 % of usage worldwide. Lead scrap (mainly lead-acid battery) is smelted in primary and secondary smelter. Most secondary lead smelting were performed in a shaft-type furnace (blast furnace), rotary furnace and reverberatory furnace. The lead bullion is either cast into ingots and re-melted in refining kettles or refining is performed on the hot lead bullion immediately after production. This work provides an overview of the primary lead production and recycling process.

• Journal of Korea Water Resources Association
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• v.56 no.spc1
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• pp.1015-1026
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• 2023

The confluence of rivers, where rivers meet, is a place known for complex water mixing dynamics. Sometimes, these rivers flow downstream without mixing. While this non-mixing can pose challenges for water quality management, it also offers the potential for improved water extraction in nearby water intakes (Chilseo). In this study, we analyzed the mixing dynamics at the confluence of the Nakdong River and the Nam River using drone imagery, water quality indicators like Electrical Conductivity, and hydraulic factor Secondary Flow. We found that meandering effects hindered mixing, as shown by the comparison of Secondary Flow and Electrical Conductivity distributions. Additionally, the Chilseo Water Purification Plant downstream of the Nakdong River-Nam River confluence extracted unmixed Nam River water during certain periods.

• Communications of Mathematical Education
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• v.38 no.2
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• pp.231-246
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• 2024

In this paper, we present the development and a case study on 'Mathematics & Coding Mobile Contents' tailored for secondary education. These innovative resources aim to alleviate the burden of laborious calculations, enabling students to allocate more time to engage in discussions and visualize complex mathematical concepts. By integrating these contents into the curriculum, students can effectively meet the national standards for achievement in mathematics. They are empowered to develop their mathematical thinking skills through active engagement with the material. When properly integrated into secondary mathematics education, these resources not only facilitate attainment of national curriculum standards but also foster students' confidence in their mathematical abilities. Furthermore, they serve as valuable tools for nurturing both computational and mathematical thinking among students.

• Journal of Korea Water Resources Association
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• v.50 no.2
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• pp.89-97
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• 2017

Turbulent flow structure in the high amplitude meandering channel is complex due to secondary recirculation with helicoidal motions and shear layers formed by flow separation from the curved sidewall. In this work, the secondary flow and the superelevation of the water surface produced in the high-amplitude Kinoshita channel are reproduced by the unsteady Reynolds-averaged Navier-Stokes (RANS) computations using the VOF technique for resolving the variation of water surface elevation and three statistical turbulence models ($k-{\varepsilon}$, RNG $k-{\varepsilon}$, $k-{\omega}$ SST). The numerical results computed by a second-order accurate finite volume method are compared with an existing experimental measurement. Among applied turbulence models, $k-{\omega}$ SST model relatively well predicts overall distribution of the secondary recirculation in the Kinoshita channel, while all three models yield similar prediction of water superelevation transverse slope. The secondary recirculation driven by the radial acceleration in the upstream bend affects the flow structure in the downstream bend, which yields a pair of counter-rotating vortices at the bend apex. This complex flow pattern is reasonably well reproduced by the $k-{\omega}$ SST model. Both $k-{\varepsilon}$ based models fail to predict the clockwise-rotating vortex between a pair of counter-rotating vortices which was observed in the experiment. Regardless of applied turbulence models, the present computations using the VOF method appear to well reproduce the superelevation of water surface through the meandering channel.

• Korean Journal of Plant Resources
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• v.35 no.5
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• pp.586-593
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• 2022

Soybean (Glycine max (L.) Merr.) is a high-protein oilseed crop, cultivated worldwide. Soybean seeds are abundant in various secondary metabolites with physiologically active. Mature seeds of 25 soybean cultivars with various morphological and physiological characteristics analyzed for secondary metabolites, such as carotenoid, isoflavone, and soyasaponin. These secondary metabolites showed various content by genotype in 25 cultivars. Total carotenoid content ranged from 1.23 to 33.78 mg/g and three cultivars, such as IT177645, PI90763 and IT234975 with black seed coat showed high levels of total carotenoid. Total isoflavones content ranged from 20.28 to 276.35 mg/100g and were detected high levels in Savoy, PI90763 and KLG16001. In addition, total soyasaponins content ranged from 33.12 to 246 mg/100g and were detected high levels in PI90763, PI86490 and IT234975. The PI90763 was showed abundant content in all of the carotenoid, isoflavones and soyasaponins. These results could be valuable information for the development of new soybean cultivars and regulation of secondary metabolites biosynthesis in soybean.

• Korean Journal of Clinical Pharmacy
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• v.28 no.1
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• pp.30-39
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• 2018

Background: Clinical Pharmacy Practice Experience (CPPE) is an important curriculum that offers students patient-centered disease prevention and treatment with evidence-based optimal pharmacotherapy for better clinical outcomes. However, few studies have evaluated the perception of pharmacy students regarding CPPE in tertiary and secondary hospitals. This study aimed to evaluate the perception of pharmacy students regarding the learning program of CPPE. Methods: The survey questionnaire consisted of 15 self-administered questions regarding pharmacy practices, barriers, and improvement of practical training. Fourteen institutional pharmacies located in seven regions responded to a survey questionnaire from March 1 to June 30, 2017. The participants were pharmacy students doing clerkship in a hospital setting. Results: The response rate was 73.6%. Thirty-five participants (22.4%) had used a hospital library, but 121 (77.6%) had never used the library for drug information resources. Eighty-one (50.0%) responded that clinical knowledge and drug information was the most beneficial practice. Thirty-seven (31.1%) respondents in the tertiary hospitals and 19 (46.3%) in the secondary hospitals answered that they were filling prescriptions during the daily break. On the other hand, 72 respondents (60.5%) in the tertiary hospitals and 17 (41.5%) in the secondary hospitals did literature research to prepare for presentation. Conclusion: More students in secondary hospitals continue to fill prescriptions during the daily break, as compared to those in tertiary hospitals. Therefore, the authors suggest self-directed learning to improve clinical performance and each institution considers offering onsite or online library service to improve evidence-based CPPE for pharmacy school students.

• Korean Journal of Metals and Materials
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• v.46 no.8
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• pp.477-481
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• 2008

The secondary hardening and fracture behavior in P/M high speed steels bearing V content of 9 to 10 wt% have been investigated in terms of austenitizing temperature and precipitation behavior. Austenitizing was conducted at 1,100 and $1,175^{\circ}C$ of relatively low and high temperatures. Coarse primary carbides retained after austenitization were mainly V-rich MC type. They give a significant influence on hardeness and toughness, as well as wear resistance. Tempering was performed in the range of $500{\sim}600^{\circ}C$. The peak hardness resulting from the precipitation of the fine MC secondary carbides was observed near 520, irrespective of austenitizing temperature. Aging acceleration(or deceleration) did not occur with increasing austenitizing temperature because it mainly influences contents of V and C of matrix through the dissloution of coarse primary MC containing lots of V and C. The precipitation of secondary MC carbides, which also contain V and C, did not change the aging kinetics itself. In the 10V alloy containing much higher C content, the impact toughness was lower than 9V alloy, because of the larger amount of primary carbide and high hardness.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.618-623
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• 2003

Solvent extraction experiments for separation of impurities from Ni-rich solution were carried out for manufacturing of high purity Ni compounds from acid leaching solution of spent Ni-Cd secondary battery. Artificial and leaching solutions were used as aqueous phases and PC88A saponified by sodium in kerosene were used as organic phase. The extraction order is Zn>Mn>Co>Ni and extraction percentage of metal ions was increased with increase of the concentration of extractant, initial pH of aqueous phase and ratio of O/A. The separation of cobalt, zinc and manganese from nickel was effectively accomplished at the condition of extraction stage=l, O/A=1 and initial pH 5.0 with 1.0 $mol/dm^3$ PC88A saponified to $50\%$ with NaOH.