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33. Novel Bis(4-aminophenoxy) Benzene-Based Aramid Copolymers with Enhanced Solution Processability.

Author

Song, Wonseong, Jadhav, Amol M., Ryu, Yeonhae, Kim, Soojin, Im, Jaemin, Jeong, Yujeong, Vanessa, Kim, Youngjin, Sung, Yerin, Kim, Yuri, and Choi, Hyun Ho

Abstract

Aramid copolymers have garnered significant interest due to their potential applications in extreme environments such as the aerospace, defense, and automotive industries. Recent developments in aramid copolymers have moved beyond their traditional use in high-strength, high-temperature resistant fibers. There is now a demand for new polymers that can easily be processed into thin films for applications such as electrical insulation films and membranes, utilizing the inherent properties of aramid copolymers. In this work, we demonstrate two novel aramid copolymers that are capable of polymerizing in polar organic solvents with a high degree of polymerization, achieved by incorporating flexible bis(4-aminophenoxy) benzene moieties into the chain backbone. The synthesized MBAB-aramid and PBAB-aramid have enabled the fabrication of exceptionally thin, clear films, with an average molecular weight exceeding 150 kDa and a thickness ranging from 3 to 10 μm. The dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) reveal that the thin films of MBAB-aramid and PBAB-aramid exhibited glass transition temperatures of 270.1 °C and 292.7 °C, respectively, and thermal decomposition temperatures of 449.6 °C and 465.5 °C, respectively. The mechanical tensile analysis of the 5 μm thick films confirmed that the tensile strengths, with elongation at break, are 107.1 MPa (50.7%) for MBAB-aramid and 113.5 MPa (58.4%) for PBAB-aramid, respectively. The thermal and mechanical properties consistently differ between the two polymers, which is attributed to variations in the linearity of the polymer structures and the resulting differences in the density of intermolecular hydrogen bonding and pi-pi interactions. The resulting high-strength, ultra-thin aramid materials offer numerous potential applications in thin films, membranes, and functional coatings across various industries. [ABSTRACT FROM AUTHOR]

Published
2024
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35. Onion (Allium cepa) Profit Maximization via Ensemble Learning-Based Framework for Efficient Nitrogen Fertilizer Use.

Author

Kim, Youngjin, Kim, Sumin, and Kim, Sojung

Subjects
*NITROGEN fertilizers, *REGRESSION analysis, *PROFIT maximization, *LABOR costs, *CROP yields
Abstract

Onion (Allium cepa) is a major field vegetable in South Korea and has been produced for a long time along with cabbage, radish, garlic, and dried peppers. However, as field vegetables, including onions, have recently been imported at low prices, the profitability of onion production in South Korea is beginning to be at risk. In order to maximize farmers' profits through onion production, this study develops onion yield prediction models via an ensemble learning-based framework involving linear regression, polynomial regression, support vector regression, decision tree, ridge regression, and lasso regression. The use of nitrogen fertilizers is considered an independent variable in the development of the yield prediction model. This is because the use of nitrogen fertilizers accounts for the highest production cost (13.47%) after labor cost (41.21%) and seed cost (17.42%), and it also directly affects onions yields. For the model development, five research datasets on changes in onion yield according to changes in the use of existing nitrogen fertilizers were used. In addition, a non-linear optimization model was devised using onion yield prediction models for the profit maximization of onion production. As a result, the developed non-linear optimization model using polynomial regression enables an increase in profits from onion production by 67.28%. [ABSTRACT FROM AUTHOR]

Published
2024
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36. Strategic Public Relations Policy for Accelerating Hydrogen Acceptance: Insights from an Expert Survey in South Korea.

Author

Cho, Minhyuk, Lee, Youhyun, Kim, Youngjin, and Lee, Min Chul

Subjects
HYDROGEN as fuel, ANALYTIC hierarchy process, PUBLIC opinion, PUBLIC support, RISK perception
Abstract

Hydrogen has great growth potential due to its green, carbon-neutral nature, but public acceptance is low due to negative perceptions of the dangers associated with hydrogen energy. Safety concerns, particularly related to its flammability and explosiveness, are an obstacle to hydrogen energy policy. In South Korea, recent hydrogen-related explosions have exacerbated these concerns, undermining public confidence. This study developed public relations (PR) strategies to manage risk perception and promote hydrogen energy acceptance by analyzing the opinions of government officials and experts using SWOT factors, the TOWS matrix, and the analytic hierarchy process. The findings highlight the importance of addressing weaknesses and threats in PR efforts. Key weaknesses include Korea's technological lag and the low localization of core hydrogen technologies, both of which hinder competitiveness and negatively impact public perception of hydrogen energy. Notable threats include deteriorating energy dependency and expanding global carbon regulations. This information can be used to influence attitudes and foster public acceptance of hydrogen energy policies. Emphasizing weaknesses and threats may result in more effective PR strategies, even if they do not directly address the primary concerns of scientific experts. The persuasive insights identified in this study can support future policy communication and PR strategies. [ABSTRACT FROM AUTHOR]

Published
2024
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