• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.35-44
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• 2022

This study aims to evaluate the stress and life of cylindrical roller bearings used in aircraft gearboxes, and to select a roller profile that minimises the contact stress between bearing rollers and raceways. The mounting clearance of four points contact ball bearing was determined, so that cylindrical roller bearings support all radial loads, and the bearing mounting position was determined to maximise the bearing lives. In addition, the static safety factor and dynamic life of bearing were predicted according to ISO 76 & ISO/TS 16281 using the load spectrum determined based on the operating load cases of aircraft gearboxes. Furthermore, the optimal roller profile was selected by analysing the contact stress according to the roller profile shape, and the safety of each roller was evaluated. The results stated that the required safety factor and lifetime were satisfied, and Johns Gohar roller profile was optimal.

• Clean Technology
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• v.28 no.4
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• pp.331-338
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• 2022

The objective of this study is to prepare bead-type and pellet-type Pt (1 wt%)/Kieselguhr catalysts as hydrogenation catalysts for the polycyclic aromatic hydrocarbons (PAHs) included in pyrolysis fuel oil (PFO). The optimal reaction temperature to maximize the yield of saturated cyclic hydrocarbons during the PFO-cut hydrogenation reaction in a trickle bed reactor was determined to be 250 ℃. A hydrogen/PFO-cut flow rate ratio of 1800 was found to maximize 1-ring saturated cyclic compounds. The yield of saturated cyclic compound increased as the space velocity (LHSV) of PFO-cut decreased. The difference in hydrogenation reaction performance between the pellet catalyst and the bead catalyst was negligible. However, the catalyst impregnated by Pt after molding the Kieselguhr support (AI catalyst) showed higher hydrogenation activity than the catalyst molded after Pt impregnation on the Kieselguhr powder (BI catalyst), which was a common phenomenon in both the pellet catalysts and bead catalysts. This may be due to a higher number of active sites over the AI catalyst compared to the BI catalyst. It was confirmed that the pellet catalyst prepared by the AI method had the best reaction activity of the prepared catalysts in this study. The majority of the PFO-cut hydrogenation products were cyclic hydrocarbons ranging from C₈ to C₁₅, and C₁₁ cyclic hydrocarbons had the highest distribution. It was confirmed that both a cracking reaction and hydrogenation occurred, which shifted the carbon number distribution towards light hydrocarbons.

• Journal of agricultural medicine and community health
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• v.47 no.4
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• pp.242-254
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• 2022

Purpose: This study was designed to test structural equation modeling of the quality of life of elderly diagnosed dementia living in the community in order to provide guidelines for development of intervention and strategies to improve their quality of life. Methods: The participants in the study were elderly who visited the public health center in C rural between May 30 and september 15, 2017. Data collection was carried out through one-on-one interviews. Demographic factors, knowledge, Attitude, Self-Efficacy, social support, accessibility, request for Information, health practice, depression, subjective memory complaints, dependence scale and quality of life were investigated. Results: The final analysis included 192 elderly. Fitness of the hypothesis model was appropriate(χ²=192.89, p=.000, GFI=0.90, SRMR=0.08, NNFI=0.94, CFI=0.95, PNFI=0.72, RMSEA=0.07). Depression, subjective memory complaints and dependence were found to be significant explaining varience in quality of life. Social support, dementia preventive behavior and health practice had an indirect effect on the quality of life. Conclusions: To improve the quality of life of elderly diagnosed dementia living in the community, comprehensive interventions are necessary to manage knowledge, attitude, self-efficacy, social support, health practice, depression, subjective memory complaints and dependence that can contribute to enchance the quality of life of elderly diagnosed dementia living in the community.

• Journal of Science Education
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• v.46 no.1
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• pp.80-92
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• 2022

We fitted latent growth models of attitude towards science using the Korea Education & Employment Panel 2004-2007 data with 343 high school students. The growth model show better fit indices compared to the no growth model. The intercept and slope showed significant variances, and thus, we added control variables of the number, ratio of advanced courses, and variety in science elective subjects, and the achievement percentile for middle school. In the conditional growth model, the previous achievement has significant positive effects on the intercept and the ratio of the advanced courses and variety of science subjects show significantly positive effects on the slope. Based on the results, it supports the 2022 Revised Science Curricular that high school credit system should provide students with basic 'Physics,' 'Chemistry,' 'Biology,' and 'Earth Science,' credits in 'general electives', various integrated subjects in 'converged electives', and highly advanced subjects in 'career electives.'

• Membrane Journal
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• v.32 no.2
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• pp.116-125
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• 2022

In this experiment, an α-Al₂O₃ ceramic hollow fiber was used as a support, and a hydrogen membrane plated with Pd and Pd-Ag was manufactured through electroless plating. The Pd-Ag membrane was annealed at 500℃ for 10 h to form an alloy of Pd and Ag. It was confirmed that it became a Pd-Ag alloy through EDS (Energy Dispersive X-ray Spectroscopy) analysis. Also, the thickness of the Pd, Pd-Ag plating layer was measured to be about 8.98 and 9.29 ㎛ through SEM (Scanning Electron Microscope) analysis respectively. Hydrogen permeation experiment was performed using the H₂ gas and mixed gas (H₂ and N₂) in the range of 350~450℃ and 1-4 bar using the prepared hydrogen membrane. Under the H₂ gas condition, the Pd and Pd-Ag membrane has a flux of up to 21.85 and 13.76 mL/cm²·min and also separation factors of 1216 and 361 were obtained in the mixed gas at 450℃ and 4 bar conditions respectively.

• Korean Association of Arts Management
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• no.56
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• pp.89-117
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• 2020

In order to secure sustainable financial resources and to attract more key supporters, today's art museums are trying to further develop individual sponsorship. The purpose of this study is to explore the direction of membership programs by considering membership as the first step for the development of individual supporters for art museums. Although it is not easy to generate substantial profits within a short period through membership, art museums can secure supporters who empathize with and participate in their mission and activities by developing individual supporters through membership. The new trends of support, which has emerged as a stream of "new philanthropy" since the 1990s, indicate that the needs and motivations of individual supporters are changing. This has great implications for the direction of the development and operation of membership programs at art museums. This study investigated the role, method, and direction of the development of individual supporters through membership by conducting a theoretical review and a case study on the membership programs and individual sponsors of art museums. In addition, the study analyzed the cases of the Cleveland Museum of Art, the Art Institute of Chicago, and the Museum of Modern Art in the United States, which have continuously attempted new approaches and improved membership programs based on a long history of membership operation and individual support, by centering on the new attributes of philanthropy, including participation and involvement, accountability, and transparency. Based on the results, implications and suggestions for Korean art museums were derived. Amid the lack of art museums' membership programs and academic research, this study has significance in exploring the direction and prerequisites for membership for the development of individual supporters.

• Korean Journal of School Psychology
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• v.18 no.1
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• pp.121-151
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• 2021

This study aimed to identify the factors that helped and hindered secondary school teachers who experienced student suicide using the concept-mapping approach. Seven South Korean middle and high school teachers were interviewed from which 113 core statements were elicited. The participants sorted these core statements into categories by meaning. Multidimensional scaling and hierarchical cluster analysis were conducted to identify the underlying structure of the teachers' experiences. Four hindering factor clusters emerged: (1) regret over failing to prevent the suicide, (2) an apathetic atmosphere in the school, (3) a sense of helplessness related to suicide survivors, and (4) approach-avoidance conflicts related to suicide survivors. Six helpful factor clusters emerged: (1) cooperation and care offered between suicide survivors, (2) focusing on the present, busy life, (3) spiritual activity, (4) social support, (5) overcoming grief through altruistic behaviors, and (6) sympathy for the deceased. Two dimensions were found for both the hindering and helpful factors. The hindering factor dimensions were external system-internal experiences and related to suicide survivors-related to suicide decedents. The helpful factor dimensions were distancing from the loss-approaching the loss and professional activities-personal activities. The present study empirically explored and described the underlying structure of teachers' bereavement experiences after student suicides.

• Clean Technology
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• v.28 no.3
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• pp.227-231
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• 2022

The demand for high-voltage power devices is rising in various industries, but especially in the transportation industry due to autonomous driving and electric vehicles. IGBT module parts of 3.3 kV or more are used in the power propulsion control device of electric vehicles, and the procurement of these parts for new construction and maintenance is increasing every year. In addition, research to optimize high-voltage IGBT parts is urgently required to overcome their very high technology entry barrier. For the development of high-voltage IGBT devices over 3.3 kV, the resistivity range setting of the wafer and the optimal conditions for major unit processes are important variables. Among the manufacturing processes to secure the optimal junction depth, the optimization of the diffusion process, which is one step of the unit process, was examined. In the diffusion process, the type of gas injected, the injection time, and the injection temperature are the main variables. In this study, the range of wafer resistance (Ω cm) was set for the development of high voltage IGBT devices through unit process simulation. Additionally, the well drive in (WDR) condition optimization of the diffusion process according to temperature was studied. The junction depth was 7.4 to7.5 ㎛ for a ring pattern width of 23.5 to25.87 ㎛, which can be optimized for supporting 3.3 kV high voltage power devices.

• Journal of Nutrition and Health
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• v.55 no.5
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• pp.572-586
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• 2022

Purpose: This study examined the factors that may affect the growth status of preterm infants. Methods: This study included 91 preterm infants born at <37 weeks of gestation (22.9-36.9 weeks of gestation), including 48 (52.7%) males and 43 (47.3%) females. Diet-related data were collected through parental questionnaires, and growth-related data, such as height and weight, were collected through the hospital medical records. Results: No significant difference in weight and growth was observed between early and late preterm infants. On the other hand, smaller averages of all weight z-score (recent weight at 40 weeks of gestation) included lower birth weight, height, and head circumference. On the other hand, infants' birth weight, height, and head circumference in the weight z-score of <0 (<50% in the age-weight growth chart) was smaller than those in the weight z-score of ≥0. Furthermore, neonatal intensive care unit (NICU) hospitalization period and NICU discharge were shorter with growth cessation age in weight z-score of <0. The weight growth velocity was associated with gestational age, birth weight, and medical treatment in the NICU. Thus, parents of preterm infants with low growth rates prefer more community care services for their children. Conclusion: Birth weight, age of preterm infants, and medical treatment in the NICU were factors related to early birth weight growth. Following NICU discharge, poor intake and intake issues were associated with poor growth after 40 weeks of gestation. Therefore, monitoring the growth of preterm infants requires continuous active involvement and supports for growth-promoting factors after NICU discharge.

• Membrane Journal
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• v.32 no.5
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• pp.292-303
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• 2022

An eco-friendly energy conversion device without the emission of pollutants has gained much attention due to the rapid use of fossil fuels inducing carbon dioxide emissions ever since the first industrial revolution in the 18th century. Polymer electrolyte membrane fuel cells (PEMFCs) that can produce water during the reaction without the emission of carbon dioxide are promising devices for automotive and residential applications. As a key component of PEMFCs, polymer electrolyte membranes (PEMs) need to have high proton conductivity and physicochemical stability during the operation. Currently, perfluorinated sulfonic acid-based PEMs (PFSA-PEMs) have been commercialized and utilized in PEMFC systems. Although the PFSA-PEMs are found to meet these criteria, there is an ongoing need to improve these further, to be useful in practical PEMFC operation. In addition, the well-known drawbacks of PFSA-PEMs including low glass transition temperature and high gas crossover need to be improved. Therefore, this review focused on recent trends in the development of high-performance PFSA-PEMs in three different ways. First, control of the side chain of PFSA copolymers can effectively improve the proton conductivity and thermal stability by increasing the ion exchange capacity and polymer crystallinity. Second, the development of composite-type PFSA-PEMs is an effective way to improve proton conductivity and physical stability by incorporating organic/inorganic additives. Finally, the incorporation of porous substrates is also a promising way to develop a thin pore-filling membrane showing low membrane resistance and outstanding durability.