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5. Interlayer Bond Strength of 3D Printed Concrete Members with Ultra High Performance Concrete (UHPC) Mix.

Author

Lee, Yoon Jung, Lee, Sang-Hoon, Kim, Jae Hyun, Jeong, Hoseong, Han, Sun-Jin, and Kim, Kang Su

Subjects
HIGH strength concrete, BOND strengths, TENSILE tests, SHEAR strength, MOLDS (Casts & casting)
Abstract

In structures manufactured using 3D concrete printing, cracks can easily propagate along the interface between printed layers. Therefore, it was necessary to determine the interlayer bond strength. In this study, direct shear and tensile tests were performed to determine the interlayer bond stability of the 3DCP members. To confirm the appropriateness of the mix proportion used to fabricate the specimens, the open time available for printing was identified via a mixing test, and the extrudability and buildability were verified via a printing test. In addition, direct shear and tensile tests were performed using the specimen manufacturing method (i.e., mold casting and 3D printing) and printing time gap (PTG) between the laminated layers as key test variables. The interlayer bond strengths of the specimens, according to the variables obtained from the test results, were compared and analyzed based on the interfacial shear strength standards presented in the current structural codes. In the direct shear test, failure occurred at the interlayers of all the specimens, and the interlayer bond strength tended to decrease with increasing PTG. In addition, the interlayer bond strength of the direct shear specimens exceeded the interfacial shear strength suggested by current structural codes. In contrast, in the direct tensile test, interlayer surface failure occurred only in some specimens, and there was no distinct change in the interlayer bond strength owing to PTG. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Variability of Glucosinolates in Pak Choy (Brassica rapa subsp. chinensis) Germplasm.

Author

Kim, Seong-Hoon, Ochar, Kingsley, Hwang, Aejin, Lee, Yoon-Jung, and Kang, Hae Ju

Subjects
BOK choy, GLUCOSINOLATES, CHINESE cabbage, GERMPLASM, BRASSICACEAE, ALIPHATIC compounds, RURAL development
Abstract

Glucosinolates are sulfur-containing phytochemicals generally abundant in cruciferous vegetables such as pak choy. Glucosinolates participate in a range of biological activities essential for promoting a healthy human body. In this study, we aimed to elucidate glucosinolate variability present in pak choy germplasm that are under conservation at the Rural Development Administration Genebank, Jeonju, Republic of Korea. The Acquity Ultra-Performance Liquid Chromatography (UHPLC) analytical system was used in profiling the glucosinolate content in leaf samples of various accessions. We identified a total of 17 glucosinolates in the germplasm. Based on principal compoment analysis performed, three separate groups of the accessions were obtained. Group 1 contained the cultivar cheongsacholong which recorded high content of glucobrassicin (an indole), glucoerucin (aliphatic), gluconasturtiin (aromatic) and glucoberteroin (aliphatic). Group 2 consisted of six accessions, BRA77/72, Lu ling gaogengbai, 9041, Wuyueman, RP-75 and DH-10, predominatly high in aliphatic compounds including glucoiberin, glucocheirolin, and sinigrin. Group 3 comprised the majority of the accessions which were characterized by high content of glucoraphanin, epiprogoitrin, progoitrin, and glucotropaeolin. These results revealed the presence of variability among the pak choy germplasm based on their glucosinolate content, providing an excellent opprtunity for future breeding for improved glucosinolate content in the crop. [ABSTRACT FROM AUTHOR]

Published
2024
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10. MRI-Based Personalized Transcranial Direct Current Stimulation to Enhance the Upper Limb Function in Patients with Stroke: Study Protocol for a Double-Blind Randomized Controlled Trial

Author

Yoo, Yeun Jie, primary, Park, Hye Jung, additional, Kim, Tae Yeong, additional, Yoon, Mi-Jeong, additional, Oh, Hyun-Mi, additional, Lee, Yoon Jung, additional, Hong, Bo Young, additional, Kim, Donghyeon, additional, Kim, Tae-Woo, additional, and Lim, Seong Hoon, additional

Published
2022
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16. The feasibility and satisfaction of an online global health education course at a single medical school: a retrospective study

Author

Lee, Su-Jin, Park, Jayoung, Lee, Yoon Jung, Lee, Sira, Kim, Woong-Han, and Yoon, Hyun Bae

Subjects
Students, Medical, undergraduate medical education, Learning community, education, Personal Satisfaction, Academic achievement, Final examination, Global Health, lcsh:Education (General), Education, Course (navigation), Education, Distance, Surveys and Questionnaires, Global health, ComputingMilieux_COMPUTERSANDEDUCATION, Humans, Schools, Medical, Original Research, Medical education, lcsh:R5-920, Academic Success, Medical school, Retrospective cohort study, online education, Course evaluation, Feasibility Studies, Psychology, lcsh:L7-991, lcsh:Medicine (General), Education, Medical, Undergraduate
Abstract

Purpose The aim of this study was to evaluate the feasibility and satisfaction of an online global health education course for medical students in comparison with an in-person of the course and to assess students' preferences regarding online methods of delivery. Methods Second-year medical students enrolled in this course in 2019 (in-person) and 2020 (online). The attendance rate, satisfaction in the course evaluation survey, and academic achievement on the written final examination were utilized to compare the two different methods of course delivery. The medical students who took the online course were also asked about their preferences regarding the method of course delivery and the advantages and drawbacks of each method of online lectures. Results There was no significant difference in the attendance rate and overall satisfaction between the two groups. The mean score on the written examination of the online course (84.1±19.6) showed comparable effects to the in-person course (78.0±18.3). The percentages of students who achieved high performance (55.5%) and the achieved minimum requirement (95.9%) were also maintained compared to the in-person course (14.6% and 93.6%, respectively). Medical students preferred the online course to the in-person course; in particular, they preferred prerecorded videos over live streaming online lectures. Conclusion The participation, satisfaction, and the academic achievement of the online course were comparable to those of the in-person course. However, the greatest drawback of the online course was the lack of interaction between peer learners. Therefore, diverse methods for online education should be considered to increase students' sense of belonging to a learning community.

Published
2020

27. Resistive Switching Memory: Lead‐Free Dual‐Phase Halide Perovskites for Preconditioned Conducting‐Bridge Memory (Small 41/2020)

Author

Ho Won Jang, Kyung Ju Kwak, Hyo Jung Kim, Soo Young Kim, Ji Su Han, In Hyuk Im, Jae-Hyun Kim, Min Kyung Lee, Kootak Hong, Da Eun Lee, Sol A Lee, Seung Ju Kim, Lee Yoon-Jung, Quyet Van Le, and Min-Ju Choi

Subjects
Materials science, business.industry, Phase (waves), Halide, General Chemistry, Bridge (interpersonal), Dual (category theory), Biomaterials, Optoelectronics, General Materials Science, Resistive switching memory, business, Lead (electronics), Biotechnology
Published
2020
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28. Rheological Property Criteria for Buildable 3D Printing Concrete

Author

Seong Tae Yi, Seung-Ho Choi, Kang Su Kim, Lee Yoon-Jung, Hoseong Jeong, and Sun-Jin Han

Subjects
0211 other engineering and technologies, 3D printing, 02 engineering and technology, Computational fluid dynamics, lcsh:Technology, Article, Rheology, 021105 building & construction, Shear stress, General Materials Science, Transformation equation, lcsh:Microscopy, Mathematics, lcsh:QC120-168.85, mixture design, lcsh:QH201-278.5, business.industry, lcsh:T, Structural engineering, 021001 nanoscience & nanotechnology, lcsh:TA1-2040, Hardening (metallurgy), concrete, rheology, lcsh:Descriptive and experimental mechanics, lcsh:Electrical engineering. Electronics. Nuclear engineering, buildability, 0210 nano-technology, business, lcsh:Engineering (General). Civil engineering (General), lcsh:TK1-9971
Abstract

Fresh concrete used in 3D printing should ensure adequate yield stress, otherwise the printed concrete layer may suffer intolerable deformation or collapse during the printing process. In response to this issue, an analytical study was carried out to derive the initial yield stress and hardening coefficient of fresh concrete suitable for 3D printing. The maximum shear stress distribution of fresh concrete was calculated using a stress transformation equation derived from the equilibrium condition of forces. In addition, the elapsed time experienced by fresh concrete during the printing processes was estimated and was then substituted into the elapsed time-yield stress function to calculate the yield stress distribution. Based on these results, an algorithm capable of deriving both the initial yield stress and the hardening coefficient required for printing fresh concrete up to the target height was proposed and computational fluid dynamics (CFD) analyses were performed to verify the accuracy of the proposed model.

Published
2019

39. Osteoclastogenesis is enhanced by activated B cells but suppressed by activated CD8+ T cells

Author

Lee Yoon-Jung, Kyung Mi Woo, Hyun-Man Kim, Byoung S. Kwon, Seong-Hee Ko, Su-Jin Park, and Youngnim Choi

Subjects
musculoskeletal diseases, medicine.medical_specialty, ZAP70, Immunology, Biology, Molecular biology, Interleukin 21, medicine.anatomical_structure, Endocrinology, Osteoclast, RANKL, Internal medicine, medicine, biology.protein, Immunology and Allergy, Cytotoxic T cell, IL-2 receptor, Activated Lymphocyte, B cell
Abstract

Host immune response is known to contribute to the progression of periodontitis, and alveolar bone destruction in periodontitis is associated with enhanced osteoclast activity. Therefore, we evaluated the roles of activated lymphocyte subsets in osteoclastogenesis. Osteoclast precursors were co-cultured with activated lymphocytes (B, CD4(+) T, CD8(+) T) in the presence of either macrophage colony-stimulating factor (M-CSF) alone or M-CSF plus soluble receptor activator of NF-kappaB ligand (sRANKL), and subsequent differentiation into active osteoclasts was evaluated by a resorption assay. The activated B and CD4(+) cells, but not CD8(+) T cells, induced osteoclast differentiation in the presence of M-CSF alone. In the presence of M-CSF and sRANKL, B cells induced the formation of small but highly active osteoclasts and increased resorption, while CD8(+) T cells profoundly suppressed osteoclastogenesis. Co-culture using an insert well or supernatant suggested that both B and CD8(+) T cells acted on osteoclasts mostly via soluble proteins. Activated B cells expressed many osteoclastogenic factors including RANKL, TNF-alpha, IL-6, MIP-1alpha, and MCP-3. CD8(+) T cells expressed a substantial amount of osteoprotegerin (OPG) along with RANKL. However, blocking antibody to OPG did not reverse the suppression by CD8(+) T cells, suggesting that other factor(s) are involved. Taken together, activated B cells promoted osteoclastogenesis, while CD8(+) T cells inhibited the osteoclast formation via direct interaction. The results imply the importance of lymphocyte subpopulations in the development of periodontitis.

Published
2001
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50. Cross-cultural differences in social identity formation through travel blogging

Author

Lee, Yoon Jung, Gretzel, Ulrike, Lee, Yoon Jung, and Gretzel, Ulrike

Abstract

Blogs are an Internet application that continues to grow in popularity. Many blogs contain travel-related postings and, thus, are of importance for researchers and practitioners in the tourism field. Differences in blog use have been found across different cultures. This study seeks to test whether social identity theory can explain some of the differences in extent and type of blog use. A sample of 120 travel blogs written by Korean and U.S. bloggers about three different destinations (Paris, Hawaii, and Tokyo) was analyzed. The results show significant differences that fit the assumptions derived from social identity theory.

Published
2014

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