• The Journal of Engineering Geology
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• v.32 no.4
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• pp.685-696
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• 2022

Although the use of pottery-making soils has a long history, its use in the pottery industry requires that physical and geotechnical properties of the materials be established to define the suitability for various purposes. The main purpose of this study is to identify the different types of clays and mineral composition and to perform the geotechnical evaluation of the clays for making pottery products. Soils investigated in this study include raw materials used for making Baekja (white porcelains), Chungja (celadons), Buncheong, Sancheong, and Johyung. Pottery-making soils are manufactured by using different types of soils and sold by individual ceramic clay company. This study includes physical tests of soil and chemical analysis of major elements using XRF and XRD instrumentation. Grain size distributions, mineralogical composition, and a range of plasticities of soils for making different types of potteries are presented. Correlations between specific type of pottery clays and geotechnical and mineralogical characteristics are determined by comparing the test results. Since quantitative research using laboratory tests for pottery-making soils are rarely performed in Korea, further research should be done in the future to improve the Korean pottery industry.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.41 no.2
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• pp.243-249
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• 1996

To formalize the mechanization technique so as to build up competitiveness on the international market, a detail survey of a 104ha size rice farm, was made. And calculated to find out how many machine of each calibre are needed. It was found that he needed : 3 farm tractors, 3 combines, 4 grain dryers, 1 speed sprayer, 100 man days of labor for sowing, application of fertilizer and herbicide, respectively. And also needed 150 man days for combine harvesting and 60 man days for disease and pest control. It was found also that well timed harvesting is critically needed to keep rice quality. Because, in case when harvesting machine was beakdown to make harvesting time extended, then the quality drops down very much and also the farm income fall very much. Therefore, it is recommended that the amount of machine needed should be prepared and they should be well maintained so that harvest be completed in time.

• Clean Technology
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• v.29 no.1
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• pp.71-75
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• 2023

In general, the presence of non-selective intercrystalline (grain boundary) defects in polycrystalline metal-organic framework (MOF) or zeolite membranes, which are known to be ca. 1 nm in size, causes lower membrane performance (selectivity) than the intrinsically expected. In this study we show that applying a thin polymeric coating of polydimethylsiloxane (PDMS) on a polycrystalline MOF membrane is effective to cap the non-selective intercrystalline defects and therefore improve membrane performance. To demonstrate the concept, first, polycrystalline UiO-66, one of Zr-based MOFs, membranes were prepared by an in-situ solvothermal growth. By controlling membrane growth condition with respect to growth temperature, we were able to obtain polycrystalline UiO-66 membranes at 150 ℃ with intercrystalline defects of which the quantity is not significant, so it can be plugged by the suggested PDMS deposition. Second, their performances were compared before and after the PDMS deposition. As expected, the PDMS deposition ended up with a noticeable increase in CO₂/N₂ ideal selectivity from 6 to 14, indicating successful intercrystalline defect plugging. However, the enhancement in CO₂/N₂ selectivity was accompanied by a significant reduction in CO₂ permeance from 5700 to 33 GPU because the PDMS deposition not only plugs defects but also forms a continuous coating on membrane surface, adding an additional transport resistance.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.484-492
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• 1994

Microstructures of Nb$_2$O$_{5}$-doped UO$_2$ pellets have been investigated during sintering under H$_2$ and $CO_2$ atmospheres. Pellets are sintered at 1$700^{\circ}C$ in H$_2$ atmosphere and at 130$0^{\circ}C$ in $CO_2$ atmosphere for 1 to 41 hr. The addison of Nb$_2$O$_{5}$ causes the formation of large pores, which shrink to some extent in H$_2$ atmosphere but very little in $CO_2$. Fine pores in the Nb$_2$O$_{5}$-doped UO$_2$ pellet are almost annihilated when sintered under H$_2$ atmosphere but little changed under $CO_2$ atmosphere. The increase in grain size due to Nb$_2$O$_{5}$ addition is much larger in H$_2$ atmosphere than in $CO_2$. Thus the enhancement of uranium diffusion in UO$_2$ due to the Nb$_2$O$_{5}$ addition is thought to be more significant in H$_2$ atmosphere. Microstructures of Nb$_2$O$_{5}$-doped UO$_2$ pellets sintered in H$_2$ atmosphere are discussed from the viewpoint of in-reactor performance. Possible defects formation due to Nb$_2$O$_{5}$ addition is discussed to explain the enhancement of uranium diffusion in H$_2$ and $CO_2$ atmospheres.> atmospheres.

• Journal of the Korean institute of surface engineering
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• v.56 no.2
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• pp.147-151
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• 2023

Transparent ZnO (100 nm thick) and ZnO/Ti/ZnO (ZTZ) films were prepared with radio frequency (RF) and direct current (DC) magnetron sputtering on the glass substrate at room temperature. During the ZTZ film deposition, the thickness of the Ti interlayer was varied, such as 6, 9, 12, and 15 nm, while the thickness of ZnO films was kept at 50 nm to investigate the effect of the Ti interlayer on the crystallization and opto-electrical performance of the films. From the XRD pattern, it is concluded that the 9 nm thick Ti interlayer showed some characteristic peaks of Ti (200) and (220), and the grain size of the ZnO (002) enlarged from 13.32 to 15.28 nm as Ti interlayer thickness increased. In an opto-electrical performance observation, ZnO single-layer films show a figure of merit of 1.4×10^-11 Ω^-1, while ZTZ films with a 9 nm-thick Ti interlayer show a higher figure of merit of 2.0×10^-5 Ω^-1.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.51-59
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• 2008

In this study, cyclic shear characterics of sand-clay mixtures were analyzed. In order to perform cyclic triaxial tests on sand clay mixtures, natural clays with activity and silica sand were mixed variously to reproduce soils with wide range of grain size compositions. Test specimens with various fines contents were prepared by the moisture compaction and pre-consolidation methods, while paying attention to the void ratio expressed in terms of the sand structure and clay structures, and undrained cyclic shear tests were performed. In the test results, cyclic shear strength decreased with increasing of sand granular void ratio below 20% of fine contents. When the granular void ratio of the test specimen exceeded the maximum void ratio of the silica sand, the clay matrix dominated the soil structure, and soil structures were not influenced by compaction energy. It was observed that, the matrix structure of the coarse particles has great effect on the undrained cyclic shear strength characteristics for sand-clay mixtures, and therefore, it is more appropriate to pay more attention to the density of the sand structure, rather than to the fines content.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.275-279
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• 2023

La_0.7Sr_0.3-xMg_xMnO₃ (LSMMO) (x=0.05~0.20) specimens are fabricated by a solid phase sintering method, and the sintering temperature and time are 1,300℃ and 2 hours, respectively. The dependence of the crystalline structure according to the amount of Mg²⁺ contents is not observed, and all specimens show a polycrystalline rhombohedral crystal structure, the X-ray diffraction (110) peaks move to the high angle side with increasing the amount of Mg²⁺ contents. LSMMO specimens exhibit a granule-shaped microstructure with an average grain size of 1 ㎛ or less. Resistivity gradually decrease as the amount of Mg²⁺ contents increased. And in the La_0.7Sr_0.1Mg_0.2MnO₃ specimen, resistivity and B_25/65-value are 36.7 Ω-cm and 394 K at room temperature, respectively. LSMMO specimens show a variable-range hopping (VRH) electrical conduction mechanism, and the negative temperature of coefficient of resistance (NTCR) is approximately 0.37~0.38%/℃.

• Journal of The Geomorphological Association of Korea
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• v.18 no.2
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• pp.25-37
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• 2011

The purpose of this study is to investigate the history of phenomenon(hereinafter called mass-movement) of movement of inorganic material originated from hillslope by denudation of hillslope surrounding the watershed during Holocen period in the Chaamgol watershed(hereinafter called study watershed) uppermost stream of Maegokcheon Cheonan-si Chungnam. To do this, for the object of allivium distributed in valley bottom of study watershed, facies analysis, radiocarbon dating and grain size analysis were conducted and geomorphological analysis on study watershed conducted together. The result is like the following. It was confirmed that over around 9,100yrBP~to recent due to a few times of mass-movement occurred in time scale of 10²~10³ years, a large quantity of inorganic material is mixed in organic material layer originated from wetland formed in valley bottom of study watershed or exists between organic material layers. And it was found that in study watershed, mass-movement occurred in instable period of hillslope after the Early Holocen existed at least 8 times (M1 period~M8 period) and wetland environment formed in the stable period of hill slope existed total 4 times (W1 period~W4 period). This analysis result will be used in the future as basic material in research of Holocen climate change of Maegokcheon watershed and in restoration of denudation process of hillslope following this.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.92-92
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• 2022

In preparation for the ever-changing climate and unification of North Korea and South Korea, it is necessary to increase the grain self-sufficiency rate by selecting crops with good utilization in high-altitude regions. The principle is to sow pastures at the end of August. However, sowing occurs in spring because the sowing period is missed when the weather is bad or when the workforce is insufficient. Sometimes when the grassland is completely devastated, it is frequently sowed in spring. In addition, North Korea consists of a high-altitude regions, and has been devastated in a general mountainous region. As a result, the landscape is not good and it is vulnerable to natural disasters such as landslides. Therefore, to prevent this, pasture must be sowed in the high-altitude regions. The goal of this study was to evaluate and compare yield and feed value of pasture species and varieties by spring sowing in high-latitude regions. The study was conducted in Pyeongchang, Gangwon-do, which is 700m height above sea level. The pasture species and varieties was sown on April 24, 2022. Each treatment was carried out by sowing 30 kg/ha, the experiment field size was 1 m²(1m×1m), and randomized block design with tri-repeat. The total of 14 varieties was used in the study, 6 varieties of Orchardgrass (OG), 6 varieties of Tall fescue (TF) and 2 varieties of Perennial ryegrass (PRG). The grassland composition fertilization using (N:P₂O₅:K₂O at 80:200:70 kg/ha) was conducted and management fertilizer was N:P₂O₅:K₂O at 210:150:180 kg/ha. The first harvest was June 26,2022 and the second harvest was on August 16, 2022. For statistical analysis of the data, an Analysis of Variance (ANOVA) was performed using the R3.6.3 software program, and all data was subjected to analysis using Duncan's multiple range test. Significance was set at the 5% level. The dry matter yield at the first harvest was the highest in PRG, and second harvest was the highest in TF (p < 0.05). Overall, PRG showed a trend of gradually decreasing growth, OG and TF showed a trend of gradually improving growth. This showed that PRG was considerably weaker to summer depression than other pasture species. Comparing the total dry matter yield, TF was the highest (4,565.45 kg/ha), but there was no significance difference with PRG (4,487.24 kg/ha) (p < 0.05). In addition, comparing the total TDN (total digestible nutrient) yield, TF was the highest (3147.33 kg/ha), second in PRG (2975.67 kg/ha) and third in OG (2052.33 kg/ha). Since this result is the data of the second harvests, if the result is derived by the end of next year, it will be provided as basic data for selection of pasture species and varieties suitable for spring seeding in high-altitude regions.

• Journal of Marine Life Science
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• v.8 no.2
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• pp.121-127
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• 2023

The study was performed in order to understand the association between organic matter content in the sediments and the distribution of macrobenthos in the intertidal zone of the Muan bay. The sediment samples obtained from 21 sampling sites in August 2019 were analyzed for sediment composition and organic matter content (Ignition loss; IL and Total organic carbon; TOC). Further the macro benthos was sorted and enumerated. The sediments of inner area of bay has coarser composition where mouth part of bay, the sediments were predominantly silty. The highest organic matter content (both of IL and TOC) was measured at station 10 located near the Mokpo area while the lowest values was measured at station 20 adjacent to the north side of the bay. The 4 most abundant species accounted for more than 10% of all specimens were Assiminea sp., Musculista senhousia, Cerithideopsilla cingulate and Heteromastus filiformis. The maximum number of species and density were observed at station 10. Cluster analysis and non-metric multidimensional scaling (MDS) allow identification of four benthic assemblages based on species abundance. The correlation analysis revealed that there was a significant difference (p<0.05) in the density with TOC. Based on the analysis; it was found that the distribution of macrobenthos varied with the differences in sediment composition and organic matter content.