• Resources Recycling
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• v.28 no.3
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• pp.26-34
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• 2019

Due to the increasing demand of rare earth magnet for various application, it is predicted that the amount of waste rare earth magnet will increase sharply. The process of waste rare earth magnet recycling is mainly consisted of leaching and separation of rare earth element contained in the magnet. However, there is no study on the breakage characteristics of the waste rare earth magnet for production of magnet powder. Therefore, in this study, effective crushing/grinding process and breakage characteristics were investigated for waste rare earth magnet. In the case of jaw crusher, the particle size of magnet was effectively reduced without rapid oxidation. In ball mill grinding test, it was found that the grinding process was not performed properly at the early stage of grinding. Moreover, waste rare earth magnet showed very low specific rate of breakage(S) and high fraction of fine particle breakage distribution(B) compared to ordinary minerals. These results can be used as a basic data for developing crushing/grinding circuit of waste rare earth magnet.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.630-637
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• 2019

The scientific, economical and industrial values of the Moon have been increased, as massive ice-water and rare resource were founded from the lunar exploration missions. Korea and other major space agencies in the world are competitively developing the ISRU (In Situ Resource Utilization) technology to secure future lunar resource as well as to construct the lunar base. To prepare for the lunar construction, it is essential to develop the rover based construction spatial information technology to provide a decision-making aided information during the lunar construction process. Thus, this research presented the construction spatial information technology based upon rover's camera system. Specifically, the conceptual design of rover based camera system was designed for acquisition of a rover's navigation image, and lunar terrain and construction images around the rover. The reference architecture of the rover operation system was designed for computation of the lunar construction spatial information. Also, rover's localization and terrain reconstruction methods were introduced considering the characteristics of lunar surface environments. It is necessary to test and validate the conceptual design of the construction spatial information technology. Thus, in the future study, the developed rover and rover operation system will be applied to the lunar terrestrial analogue site for further improvements.

• Membrane Journal
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• v.28 no.6
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• pp.424-431
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• 2018

The gas separation performance of a mixed membrane structure based on a mixture of polyethersulfone (PES) and cobalt tetraphenylporphyrin-benzylimidazole (CoTpp-BIm) as an oxygen carrier was investigated. The CoTpp-BIm mixed PES membrane had an asymmetric structure with a mixture of finger structure and sponge-like structure, and the upper surface was dense. The gas separation performance test was carried out using $94%\;N_2$ gas and $6%\;O_2$ mixed gas. Oxygen and nitrogen permeability coefficients were measured at ${\Delta}P$ ranging from 15 to 228 cmHg and the permeate side of the PES membrane was maintained at vacuum level. The oxygen permeability coefficient of CoTpp-BIm mixed PES membranes increased as supplied pressure was decreased. When the supply pressure was 15 cmHg, the gas permeability ($P_{O_2}$) was 6676 Barrer, the $O_2/N_2$ selectivity (${\alpha}$) was 6.1, and the promoting factor (F) was 2.39. Based on these results, it was confirmed that the addition of CoTpp-BIm to the PES film improved the oxygen separation characteristics.

• Journal of Korean Physical Therapy Science
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• v.28 no.2
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• pp.57-64
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• 2021

Background: During squat exercises, Ankle joint stability during squat movement transfers forces produced by unstable supports or various loads to the leg joints and trunk, reducing the risk of injury; therefore, a reference is needed for correct ankle joint posture during squat exercises. The purpose of this study was to examine the effect of ankle joint stability on quadriceps femoris and hamstring activation during squat exercises. Design: Quasi-experiment one group pretest-posttest design. Methods: The participants in this study were 20 volunteers who performed squat exercises with and without kinesiology tape. We measured quadriceps femoris and hamstring activation using surface electromyography. The ankle joint was stabilized with kinesiology tape using the ankle balance taping (ABT) method. A paired t-test was performed to compare differences between taping conditions. Results: Vastus medialis and vastus lateralis activation were greater following squat exercises with kinesiology tape than without; however, the difference was not significant. Medial and lateral hamstring activation was not significantly different between taping conditions. Conclusion: Although it is difficult to maintain stability using kinesiology tape alone, ankle joint stability is believed to affect quadriceps femoris muscle activity, which increases the effectiveness of the squat exercise.

• Journal of radiological science and technology
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• v.44 no.2
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• pp.85-90
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• 2021

The purpose of this study is to consider usefulness of using AEC mode and importance of patient center location in L-spine lateral radiography by comparing dose and image quality according to the change of patient center location with using AEC mode or not. In this study, guide wire is attached to the human body phantom's lumbar spine and the lead ruler is attached to the bottom of the wall detector to find out center location in detector. ESD, mAs, and EI were selected as dose factors, and image quality was compared through SNR. With the lumbar spine located center of the detector, dose factors and image quality were compared according to using AEC mode or not. Afterwards, phantom moved 4 cm and 8 cm back and forth and compared dose factors and image quality. The exposure parameters were 85 kVp, 320 mA, x-ray field size 10×17 inch, and the distance between the center X-ray and the detector was fixed at 100 cm. The center X-ray was perpendicular to the fourth lumbar spine and the only bottom AEC chamber was used. All data were analyzed by independent t-test and ANOVA. As a result of this study, with AEC when the center is matched, ESD was 1.31±0.01 mGy, without AEC was 2.12±0.01 mGy. SNR was shown to be 22.81±1.83, and 23.44±1.87 respectively. When the phantom's center moves 4 cm, 8 cm forward, and 4 cm, 8 cm backward, ESD were 1.09±0.004 mGy, 0.32±0.003 mGy, 1.19±0.017 mGy, 1.11±0.006 mGy respectively, SNR were 18.29±0.60 dB, 11.11±0.22 dB, 18.98±0.80 dB, 17.71±0.82 dB. Using AEC in L-spine lateral radiography reduced ESD by 38%, EI by 35%, and mAs by 38%, without any difference in SNR(p<0.05). When the phantom's center moves 4 cm, 8 cm forward, and 4 cm, 8 cm backward, ESD was decreasing each 16%, 75%, 9%, 15%, EI was decreasing each 14%, 77%, 15%, 20%, mAs was decreasing each 15% 75% 9%, 15%. SNR was decreasing each 19%, 51%, 17%, 22%.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.381-393
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• 2021

Physical, mechanical, hydraulic, and geophysical tests were applied to validate methods of inspecting the effectiveness of grouting on an agricultural reservoir dam. Data obtained from series of in situ and laboratory tests considered four stages: before grouting; during grouting; immediately after grouting; and after aging the grouting for 28 days. The results of SPT and triaxial tests, including the unit weight, compressive strength, friction angle, cohesion, and N-value, indicated the extent of ground improvement with respect to grout injection. However, they sometimes contained errors caused by ground heterogeneity. Hydraulic conductivity obtained from in situ variable head permeability testing is most suitable for identifying the effectiveness of grouting because the impermeability of the ground increased immediately after grouting. Electric resistivity surveying is useful for finding a saturated zone and a seepage pathway, and multichannel analysis of surface waves (MASW) is suitable for analyzing the effectiveness of grouting, as elastic velocity increases distinctly after grouting injection. MASW also allows calculation from the P- and S- wave velocities of dynamic properties (e.g., dynamic elastic modulus and dynamic Poisson's ratio), which can be used in the seismic design of dam structures.

• Korean Journal of Plant Resources
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• v.32 no.4
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• pp.282-289
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• 2019

Gastritis is an inflammatory disease involving the stomach and is caused by several factors, including stress, non-steroidal anti-inflammatory drugs such as aspirin, liquor, and Helicobacter pylori. In Korea, Leonurus japonicus Houttuyn (LJW) has been used as traditional medicine for vaginal bleeding, hematuria, and bruise. Previous studies have reported that LJW exhibited hepatoprotective, cardioprotective, and anti-hyperlipidemic effect. However, the effect of the water extract of LJW on gastritis was not elucidated. Thus, we evaluated the anti-gastric effect and genotoxicity of LJW. LJW effectively prevented the degeneration of surface mucous cells and glandular epithelial cells and vascular congestion induced by HCl/EtOH. Micronucleus assay indicated that the rate of micronucleated polychromatic erythrocytes/polychromatic erythrocytes was not significantly different compared that of the control. Further experiments are required to determine the role of LJW in the gastric injury process such as cyclooxygenase signaling pathway and the secretion of mucus in the stomach.

• Research in Plant Disease
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• v.26 no.4
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• pp.256-263
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• 2020

Incidence of Fusarium wilt was surveyed in fields of summer radish in Gangwon province in Korea in 2018 and 2019. The disease started in early July and spread rapidly in hot summer of late July and August and in severe case, reached up to 80% in a field in Gangneung area. Symptoms in the seedling stage include poor growth and browning of internal tissue of root. During mid-growth, the leaves of diseased plant turned yellow over time, the surface of the roots changed from white to blackish, and the vascular tissues turned brown. A total of 23 isolates was obtained from the diseased plants and identified as Fusarium oxysporum f. sp. raphani by elongation factor-1α and intergenic spacer sequence analysis. Pathogenicity of the isolates was tested by artificial inoculation to the radish and other plants. All the isolates tested were pathogenic to radish plant, although there were differences in virulence on radish 11 cultivars. However, the isolates were not virulent to other plants except some cruciferous vegetables including Brussels sprouts, rocket, stock, and turnip. The results of pathogenicity test showed that it is necessary to rotate with crops other than cruciferous vegetables in order to prevent Fusarium wilt from radish fields.

• Korean Journal of Construction Engineering and Management
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• v.22 no.1
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• pp.81-89
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• 2021

In recent years, the design of buildings is changing from formal to creative and freeform. Accordingly, the scale of construction technology is changing to architectural design and construction of irregular buildings. Using the FDM method, which is one of the 3D printing technologies, it is possible to manufacture various forms of irregular formwork inexpensively and quickly coMPared to the existing formwork, and it seems to be able to solve the manpower problem. Using a 3D printer, the PLA filament formwork is produced in the form of a cylinder and a rectangular cuboid, and the usability of the PLA filament formwork is confirmed by examining the compression strength test and the degree of deformation and reusability over 28 days of age. Different sizes of additional specimens are also conducted according to the size. As a result of the experiment, it was confirmed that the filament formwork itself has about 3~4MPa strength. As a result of reviewing data through existing linear studies and experiments, it is appropriate to use more than 60% infill, and it is advantageous in terms of strength. As a result of cutting and dismantling the filament formwork, the surface is very clean and there is no damage, so it can be reused.

• Journal of the Korean GEO-environmental Society
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• v.12 no.3
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• pp.55-61
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• 2011

Song-Do international city is the area developed in large-scale land reclamation. Song-Do area consists of reclamation layer, sedimentary layer(loose silt, soft clay and sand alternating) and residual layer from the ground surface. Therefore, using pile foundation is inevitable to build structures safely. In this area, driven PHC piles have been generally constructed in terms of environmental and economic conditions. As a result of analyzing 4 sites in Song-Do district 5 and 7 recently, the method of driving pile has many problems because of existence of rigid soil in sedimentary layer and installation of more than 30m piles. In this case, when installing piles by drive after pre-boring up to appropriate depth, the results of constructability analysis were very good. And in the economic efficiency, although 4% of construction cost rose, it was a very slight increase in comparison with improvement of workability. In the case of the stability, more than 70% compared to the allowable stress of piles was satisfied through the load test. As a result, when PHC piles is installed in Song-Do district, the proper construction method is that piles are located at bearing layer after boring rigid sand layer.