• Structural Engineering and Mechanics
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• v.81 no.3
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• pp.349-365
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• 2022

Steel fibre-reinforced concrete (SFRC) is an emerging class of composite for construction. However, a reliable method to assess the flexural behaviour of SFRC structural member is in lack. An analytical technique is proposed for determining the moment-curvature response of concrete beams reinforced with steel fibres and longitudinal bars (R/SFRC members). The behaviour of the tensile zone of such members is highly complex due to the interaction between the residual (tension softening) stresses of SFRC and the tension stiffening stresses. The current study suggests a transparent and mechanically sound method to combine these two stress concepts. Tension stiffening is modelled by the reinforcement-related approach assuming that the corresponding stresses act in the area of tensile reinforcement. The effect is quantified based on the analogy between the R/SFRC member and the equivalent RC member having identical geometry and materials except fibres. It is assumed that the resultant tension stiffening force for the R/SFRC member can be calculated as for the equivalent RC member providing that the reinforcement strain in the cracked section of these members is the same. The resultant tension stiffening force can be defined from the moment-curvature relation of the equivalent RC member using an inverse technique. The residual stress is calculated using an existing model that eliminates the need for dedicated mechanical testing. The proposed analytical technique was validated against test data of R/SFRC beams and slabs.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.2000-2010
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• 2021

Mechanical moduli, such as Young's modulus (E), Bulks modulus (B), Shear modulus (S), longitudinal modulus (L), Poisson's ratio (σ) and micro Hardness (H) were theoretically calculated for (100-x)TeO₂+x MgO glasses, where x = 10, 20, 30, 40 and 45 mol%, based on the Makishima-Mackenzie model. The estimated results showed that the mechanical moduli and the microhardness of the glasses were improved with the increase of the MgO contents in the TM glasses, while Poisson's ratio decreased with the increase in MgO content. Moreover, the radiation shielding capacity was evaluated for the studied TM glasses. Thus, the linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), transmission factor (TF) and half-value thickness (𝚫_0.5) were simulated for gamma photon energies between 0.344 and 1.406 MeV. The simulated results showed that glass TM10 with 10 mol % MgO possess the highest LAC and varied in the range between 0.259 and 0.711 cm^-1, while TM45 glass with 45 mol % MgO possess the lowest LAC and vary in the range between 0.223 and 0.587 cm^-1 at gamma photon energies between 0.344 and 1.406 MeV. Furthermore, the BXCOM program was applied to calculate the effective atomic number (Z_eff), equivalent atomic number (Z_eq) and buildup factors (EBF and EABF) of the glasses. The effective removal cross-section for the fast neutrons (ERCSFN, ∑_R) was also calculated theoretically. The received data depicts that the lowest ∑_R was achieved for TM10 glasses, where ∑_R = 0.0193 cm² g^-1, while TM45 possesses the highest ERCSFN where ∑_R = 0.0215 cm² g^-1.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.167-174
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• 2021

This study examined the influences of participation in the free semester on school life satisfaction and interest in classes and whether the effect persisted longitudinally. The participants were students from middle schools located in large cities: 451 students in the experimental group and 466 students in the control group. Only the students of the experimental group participated in the free semester. The data were collected at the end of the free semester for three years, and the results are as follows. First, the school life satisfaction of students in the experimental group was significantly higher than those in the control group until the second year but not in the third year. Second, there was no difference in interest in the main subject classes between the experimental and control groups until the third year. Third, students' interest in art and sports classes in the experimental group was significantly higher than those in the control group until the second year but not in the third year. These findings suggest that long-term planning and management of the institution rather than short-term introduction is required for the continuous effects of the free semester.

• Journal of Korean Academic Society of Home Health Care Nursing
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• v.29 no.3
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• pp.288-300
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• 2022

Purpose: This study aimed to investigate the association of social participation and depressive symptoms with health-related quality of life (HRQoL) among older adults living in urban and rural areas. Methods: This secondary, cross-sectional study was conducted with a total of 66,765 adults aged ≥65 years (urban-26,485 and rural-40,280) who participated in the household and individual surveys of the Korea Community Health Survey 2019. Data on the main study variables including social participation, depressive symptoms, and HRQoL were collected from August 16 to October 31, 2019. Multiple linear regression was used to identify the factors affecting HRQoL in urban and rural older adults. Results: The proportion of social participation (χ²=354.69, p<.001) and the level of HRQoL (χ²=12.06, p<.001) were significantly higher in older adults living in urban area than those in rural area. However, there was no significant difference in depressive symptoms between older adults living in urban and rural areas. Multiple linear regression analysis showed that social participation and depressive symptoms were significant predictors of HRQoL in both urban and rural older adults. Conclusion: Our main finding highlights that active participation in social activities and management of depressive symptoms in older adults regardless of living arrangements are crucial to improve HRQoL in later life. Interventions to increase social participation include early assessment of depressive symptoms in the community to promote HRQoL. More longitudinal studies are needed to identify the factors associated with HRQoL between older adults living in urban and rural areas while considering neighborhood environment and living arrangements.

• Journal of Periodontal and Implant Science
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• v.52 no.2
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• pp.91-115
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• 2022

Purpose: This systematic review aimed to compare the efficacy, defined in terms of the mean percentage of root coverage (mRC), of surgical treatment approaches combined with adhesive restorations of non-carious cervical lesions (NCCLs) to that of root coverage alone in patients with a single gingival recession (GR) and NCCL. Methods: A literature search was conducted to identify longitudinal studies reporting the mRC following treatment for the correction of GR defects associated with NCCLs using a combination of surgical and restorative techniques in systemically and periodontally healthy patients. Results: The search resulted in the retrieval of 12,409 records. Seven publications met the inclusion criteria for the qualitative synthesis of data. The mRCs ranged from 69% to 97%. In the medium term, the gingival margin position was more stable when a connective tissue graft (CTG) was used, independently of whether restoration of teeth with NCCLs was performed. Conclusions: The strength of the evidence was limited by methodological heterogeneity in terms of study design as well as the unit and period of analysis, which precluded a metaanalysis. Although no definitive conclusion could be drawn due to the lack of sufficient evidence to estimate the effectiveness of the interventions, CTG-based procedures contributed to gingival margin stability regardless of the performance of restoration to treat NCCLs.

• The Journal of Korean Society for School & Community Health Education
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• v.23 no.1
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• pp.17-27
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• 2022

Objectives: This longitudinal study was done to identify the relationship of school adjustment and sponsor support or future time perspective and the differences of these 3 variables between 1st and 2nd survey of children having Didimseed account in institutional care. Methods: Participants were 25 elementary fourth to sixth grade children who are living on one facility that located in G. metropolitan area at 1st survey and 2nd survey was done at five-year intervals. Data were collected from September 2012 to September 2017 and were analyzed using t-test, paired t-test, ANOVA, post-hoc test and Pearson's correlation coefficients. Results: The level of school adjustment knowledge was not different significantly according to grade, gender and admission period at 1st survey. At 2nd survey, the level of school adjustment was different significantly according to grade only. The level of school adjustment was associated with positive future time perspective(r=.74) and negative future time perspective(r=-.54) at 1st survey, and that was associated with negative future time perspective(r=-.49) and meeting frequency of sponsor(r=-.43) at 2nd survey. There were not significantly different school adjustment and future time perspective variables between both surveys. But meeting frequency of sponsor at 2nd survey was lower significantly than that at 1st survey. Conclusions: Based on the results of this study, it would be necessary to prepare the policies that could have their positive future time perspective to increase school adjustment of institutionalized children. Also the effective strategies to increase not only Didimseed account support but emotional support through qualified meeting with sponsors should be developed.

• Research in Community and Public Health Nursing
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• v.33 no.3
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• pp.299-311
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• 2022

Purpose: Untreated depression in adolescents affects their entire life. It is important to detect and intervene early depression in adolescence considering the characteristics of adolescent's depressive symptoms accompanied by internalization and externalization. The aim of this study was to identify latent classes of depressive symptom trajectories of adolescents and determinants of classes in Korea. Methods: The three time-point (2018~2020) data derived from the Korean Children and Youth Panel Survey 2018 were used (N=2,325). Latent Growth Curve Modeling (LGCM) was conducted to explore the depressive symptom trajectories in all adolescents, and Latent Class Growth Modeling (LCGM) was conducted to identify each latent class. Multinomial logistic regression analysis was performed to confirm the determinants of each latent class. Results: The LGCM results showed that there was no statistically significant change in all adolescents' depressive symptoms for 3 years. However, the LCGM results showed that four latent classes showing different trajectories were distinguished: 1) Low-stable (intercept=14.39, non-significant slope), 2) moderate-increasing (intercept=19.62, significantly increasing slope), 3) high-stable (intercept=26.30, non-significant slope), and 4) high-rapidly decreasing (intercept=26.34, significantly rapidly decreasing slope). The multinomial logistic regression analysis showed that the significant determinants (i.e., gender, self-esteem, aggression, somatization, peer relationship) of each latent class were different. Conclusion: When screening adolescent's depression, it is necessary to monitor not only direct depression symptoms but also self-esteem, aggression, somatization symptoms, and peer relationships. The findings of this study may be valuable for nurses and policy makers to develop mental health programs for adolescents.

• Human Ecology Research
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• v.60 no.3
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• pp.471-481
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• 2022

This study aimed at examining the mediation effects of depressive symptoms on the association between social activity participation and marital satisfaction among couples in later life. The study included 1,196 married couples aged 65 or above who participated in the 7th Korean Longitudinal Study of Aging in 2018. The study variables were husbands' and wives' social activity participation, marital satisfaction, and depressive symptoms. Covariates were individual age, education level, subjective health, couples' household income, and number of children. The Actor-Partner Interdependence Mediation Model (APIMeM) and bootstrapping techniques were used to test the significance of the mediating impacts of depressive symptoms based on the dyadic data structure. The results showed that for both husbands and wives, active participation in social activities had significant effects on increasing marital satisfaction through lowering depressive symptoms. However, only the participation of husbands in social activities was positively associated with their own marital satisfaction by reducing their own and their partner's depressive symptoms. These findings suggest that the active social participation of individuals salient for promoting the quality of marital relationships in later life, particularly for preventing their own and their spouse's depressive symptoms.

• Journal of the Korean Society for Library and Information Science
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• v.57 no.1
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• pp.45-68
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• 2023

The purpose of this study is to longitudinally analyze impact factors on library use. One of library use indicators, the number of circulated books was statistically analyzed with latent growth model and growth mixture model. Library data from 2014 to 2019 were collected from the National Library Statistics System, and 846 public libraries were analyzed. As results, the number of circulated books were decreased, but it was tempered. Next, with controlling the factor affecting the dependent variable, the size of collection and the number of participants in reading programs provided by public libraries were statistically significant. Lastly, 5 classes were identified by applying the growth mixture model, and the number of librarians was significantly associated with trajectory class membership.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.2
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• pp.129-138
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• 2023

The proportion of agricultural products handled through the Agricultural Products Processing Center (APC) is also steadily increasing every year, and in the case of Seongju Korean melon, a total of 10 APCs of Nonghyup and farming association corporations are in operation, and the distribution ratio is about 60% based on total production. In this study, Seongju Korean melon was selected as a target to analyze the environment load during carrying (production farm ~ APC) in the production area and the transport environment load during distribution of domestic fruits, and to analyze the environmental load for handling at APC. The vertical average vibration intensity (overall G_rms of 1~250 Hz) of truck transport measured at three transport routes from Seongju Korean melon producer ~ APC, Seongju ~ Seoul and Seongju ~ Jeju was about three times larger than that in the lateral direction and 4.5 times larger than that in the longitudinal direction, respectively. The frequency of occurrence of high-amplitude events (G) in the vertical direction compared to the measuring time was deeply related to pavement conditions in the order of unpaved farm-roads, concretepaved farm-roads, and asphalt-paved main-roads, but overall G_rms for the entire frequency band is believed to have a greater impact on vehicle traveling speed than road conditions. On the other hand, the difference in the size and direction of the vibration intensity measured by the forklift truck's main-body and the attachment (fork carrier) during handling at Seongju Korean melon APC was clear, and the vibration intensity of the forklift truck's main-body was largely affected by the stiffness of the fork and the mast according to the handling weight. Based on the field-data of the transport environment during domestic distribution measured through this study, it is believed that it is possible to develop a lab-based simulation protocol for appropriate packaging design.