• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.154-160
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• 2021

Recently, there have been increasing construction works carried out in urban centers, which are inducing frequent artificial vibration in the vicinity of existing structures due to such construction works. moreover, in case of industrial estates, vibration is induced due to operation of machines in the surrounding areas, thereby causing problems. meanwhile, in case of ordinary concrete that compose structure has low level of damping capability for vibration. accordingly, there are difficulties in blocking a wide range of vibrations delivered to the structures from outside including not only vibrations generated in the structures themselves but also ground vibration. recently, numerous studies are being carried out actively on high-damping system that markedly enhanced the damping performances of structures by utilizing polymer concrete in order to block the vibrations delivered to the structures through ground. therefore, this study compared the performances of polymer concrete with those of ordinary concrete, polyurethane pad and foamed rubber pad in order to review its performances in reducing ground vibration. for this purpose, review of FRF and vibration acceleration as dynamic characteristics was made. after comparative verification on the dynamic characteristics is made when polymer concrete and other aforementioned materials are applied to underground structures, the possibility of application of polymer concrete to structures is reviewed.

• Journal of Science Education
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• v.45 no.3
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• pp.336-348
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• 2021

The goal of this study is to investigate the current status of implementation of convergence education in elementary, middle, and high schools. A survey was conducted on 871 in-service teachers nationwide, and frequency analysis was conducted by school level. Key findings are as follows: first, 449 (51.5%) are found to practice convergence education. Second, the reason for implementing convergence education is the voluntary effort of teachers and the educational necessity for the future society. Third, it was found that convergence education is being implemented centered on science, arts, and social studies as a link between subjects in regular curriculum hours. Fourth, 270 (64%) of teachers who implemented convergence education in response to COVID-19 performed online convergence education, and experienced difficulties in creating class materials and communicating with students. Fifth, the excessive work of teachers, insufficient support for teacher training and research group activities, and lack of various convergence education programs are suggested as reasons for not implementing convergence education. This study hopes to provide implications for policy and implementation for revitalizing convergence education.

• Journal of the Korean Geotechnical Society
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• v.38 no.11
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• pp.69-86
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• 2022

The railway is widely used to transport passengers and freight due to its punctuality and large transport capacity. The recent remarkable development in construction technology enables various subsea railway tunnels for continent-continent or continent-island connectivity. In Korea, design and construction experience is primarily based on the successful completion of the Boryeong subsea tunnel (2021) and the Gadeok subsea tunnel (2010). However, frequent earthquakes with diverse magnitudes, globally induced and continuously increased the awareness of seismic risks and the frequency of domestic earthquakes. The effect of an earthquake on the subsea tunnel is very complicated. However, ground conditions and seismic waves are considered the main factors. This study simulated four ground types of 3-dimensional numerical models, such as soil, rock, composite, and fractured zone, to analyze the effect of ground type and seismic wave. A virtual subsea railway shield tunnel considering external water pressure was modeled. Further, three different seismic waves with long-term, short-term, and both periods were studied. The dynamic analyses by finite difference method were performed to investigate the displacement and stress characteristics. Consequently, the long-term period wave exhibited a predominant lateral displacement response in soil and the short-term period wave in rock. The artificial wave, which had both periodic characteristics, demonstrated predominant in the fractured zone. The effect of an earthquake is more noticeable in the stress of the tunnel segment than in displacement because of confining effect of ground and structural elements in the shield tunnel. 

• Korean Journal of Exercise Nutrition
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• v.24 no.2
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• pp.30-37
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• 2020

[Purpose] The present study investigated the effect of endurance exercise with blood flow restriction (BFR) performed at either 25% maximal oxygen uptake (${\dot{V}}O_2$ max) or 40% ${\dot{V}}O_2$ max) on muscle oxygenation, energy metabolism, and endocrine responses. [Methods] Ten males were recruited in the present study. The subjects performed three trials: (1) endurance exercise at 40% ${\dot{V}}O_2$ max without BFR (NBFR40), (2) endurance exercise at 25% ${\dot{V}}O_2$ max with BFR (BFR25), and (3) endurance exercise at 40% ${\dot{V}}O_2$ max with BFR (BFR40). The exercises were performed for 15 min during which the pedaling frequency was set at 70 rpm. In BFR25 and BFR40, 2 min of pressure phase (equivalent to 160 mmHg) followed by 1 min of release phase were repeated five times (5 × 3 min) throughout 15 minutes of exercise. During exercise, muscle oxygenation and concentration of respiratory gases were measured. The blood samples were collected before exercise, immediately after 15 min of exercise, and at 15, 30, and 60 minutes after completion of exercise. [Results] Deoxygenated hemoglobin (deoxy-Hb) level during exercise was significantly higher with BFR25 and BFR40 than that with NBFR40. BFR40 showed significantly higher total-hemoglobin (total-Hb) than NBFR40 during 2 min of pressure phase. Moreover, exercise-induced lactate elevation and pH reduction were significantly augmented in BFR40, with concomitant increase in serum cortisol concentration after exercise. Carbohydrate (CHO) oxidation was significantly higher with BFR40 than that with NBFR40 and BFR25, whereas fat oxidation was lower with BFR40. [Conclusion] Deoxy-Hb and total Hb levels were significantly increased during 15 min of pedaling exercise in BFR25 and BFR40, indicating augmented local hypoxia and blood volume (blood perfusion) in the muscle. Moreover, low-and moderate-intensity exercise with BFR facilitated CHO oxidation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.167-174
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• 2022

The objective of this study is to evaluate the dynamic properties of DUS (damping-up system) composed of the materials with excellent damping capacity, and to compare with those of the conventional hangar bolt. The main parameters are the type and hardness (𝜂_H), of rubber and the prestress force (value converted from the compression strain (𝜂_R) in the stress-strain relationship of rubber). The dynamic properties were examined from the natural frequency (𝜔_n), maximum response acceleration (A_m), amplification coefficient (𝛼_p), maximum relative displacement (𝚫_m), and damping ratio (𝜉_D). The test results showed that the A_m, 𝛼_p, and 𝚫_m values of DUS were 46.3%, 46.6% and 62.9% lower, respectively, and the 𝜉_D value was 3.89 times higher, when compared to those of the conventional hangar bolt. In particular, the 𝛼_p value was 1.3 for DUS, and 2.45 for the conventional hanger bolt, which were similar to those of rigid and flexible components specified in KDS 41 17 00, respectively. Consequently, in the optimal details of DUS, the 𝜂_H values of 50 and 45 were required for the NR (natural rubber) and EPDM (ethylene propylene diene monomer), and the 𝜂_R value of 5% was also recommended.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.3
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• pp.29-38
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• 2022

In this study, the shaking table tests were carried out on six types of non-structural elements installed on a full-scale two-story steel structure. The shaking table tests were performed for non-structural elements with and without seismic isolators. In this study, the seismic performance of Uninterruptible Power Supply (UPS) specimens was tested and investigated. Non-seismic details were composed of conventional channel section steel beams, and the seismic isolators were composed of high damping rubber bearing (HDRB) and wire isolator. The input acceleration time histories were artificially generated to satisfy the requirements proposed by the ICC-ES AC156 code. Based on the test results, the damage and dynamic characteristics of the UPS with the seismic isolator were investigated in terms of the natural frequency, damping ratio, acceleration time history responses, dynamic amplification factors, and relative displacements. The results from the shaking table showed that the dynamic characteristics of the UPS including the acceleration response were significantly improved when using the seismic isolator.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.397-404
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• 2022

This study aims to examine the effects of college students' teaching-friendly learning activities on college life adaptation, and to examine whether these effects differ according to learner characteristics. To this end, 214 people who participated in the learning program of universities located in G area in the first semester of 2022 were targeted. In order to find out the effect of teaching-friendly learning activities on college students' adaptability to college life, frequency analysis, response sample t-verification, and one-way analysis of variance (one-way Anova) were conducted using SPSS 20.0. The results are as follows. First, it was found that teaching-friendly learning activities significantly increased the scores of academic adaptation, emotional adaptation, and social adaptation in college life adaptation. Second, there was no difference in adaptation to college life according to college. Third, The score of the level of attachment to universities was found to be higher in the female group than in the male group. Fourth, as a result of the analysis according to the grade, it was found that the third-grade group had a high level of attachment to universities. Conclusions and suggestions for these research results were presented.

• Journal of the Korean Society for information Management
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• v.39 no.3
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• pp.241-261
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• 2022

The present study aims to investigate the effects of information poverty on North Korean refugees' social adaptation to South Korea based on Chatman's Theory of Information Poverty (1996). Based on the Theory of Information Poverty, information poverty consists of four variables: Secrecy, Deception, Risk-taking, and information acceptance in response to situational relevance. And based on the previous studies, adaptation to South Korean life is divided into social adaptation and psychological adaptation. From August 4 to August 30, 2021, after approval by the IRB through the North Korean refugee support organization , surveys were conducted with North Korean refugees who had lived in South Korea for at least one year and were aged 19 or older. The 100 collected valid data were analyzed using frequency analysis, reliability analysis, correlation analysis, and multiple linear regression analysis. Findings of the study indicated that information poverty had significant effects on North Korean refugees' social and psychological adaptation. In particular, the "deception" variable had negative effects on social and psychological adaptation. The study has theoretical implications that it explains North Korean refugees' adaptation to South Korea based on Theory of Information Poverty by defining them as information poor. Above all, it attempts a quantitative approach through operationalization of key concepts unlike previous studies that were conducted with qualitative approaches.

• Journal of Industrial Convergence
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• v.21 no.1
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• pp.159-165
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• 2023

While the frequency of seismic occurrence has been increasing recently, the domestic seismic response system is weak, the objective of this research is to compare and analyze the seismic vulnerability of buildings using statistical analysis and machine learning techniques. As the result of using statistical technique, the prediction accuracy of the developed model through the optimal scaling method showed about 87%. As the result of using machine learning technique, because the accuracy of Random Forest method is 94% in case of Train Set, 76.7% in case of Test Set, which is the highest accuracy among the 4 analyzed methods, Random Forest method was finally chosen. Therefore, Random Forest method was derived as the final machine learning technique. Accordingly, the statistical analysis technique showed higher accuracy of about 87%, whereas the machine learning technique showed the accuracy of about 76.7%. As the final result, among the 22,296 analyzed building data, the seismic vulnerabilities of 1,627(0.1%) buildings are expected as more dangerous when the statistical analysis technique is used, 10,146(49%) buildings showed the same rate, and the remaining 10,523(50%) buildings are expected as more dangerous when the machine learning technique is used. As the comparison of the results of using advanced machine learning techniques in addition to the existing statistical analysis techniques, in spatial analysis decisions, it is hoped that this research results help to prepare more reliable seismic countermeasures.

• Journal of the Korean Dietetic Association
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• v.29 no.3
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• pp.173-189
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• 2023

This study aimed to determine foodservice and hygiene management statuses at welfare facilities catering to disabled persons by facility type to provide basic data for foodservice management guidelines. An online survey was distributed to workers at 1,984 welfare facilities for disabled persons in Korea, and 531 facilities responded, which represented a response rate of 26.8%. The survey requested general information about the facilities, facility users, meals, hygiene, and management. Statistical analyses were performed, and frequency analysis and the chi-square test were used to investigate responses by facility type. The survey results revealed that daycare centers were most common and accounted for 27.4% of responses. Residential facilities for the severely disabled and sheltered workshops accounted for 16.9% and 16.4%, respectively, and residential facilities by disability type accounted for 13.0%. The presence of dietitians at welfare facilities varied by facility type. Welfare centers for the disabled (94.7%) had the highest percentage of dietitians, followed by residential facilities for the severely disabled (87.8%). On the other hand, sheltered workshops and daycare centers for disabled persons had the lowest percentages of dietitians (10.3% and 4.1%, respectively). This study highlights the variations that exist in foodservice management across different welfare facilities for disabled persons and emphasizes the challenges faced by those responsible for managing foodservices and maintaining hygiene, particularly in large facilities with no dietitians. Therefore, we recommend tailored meal management guidelines be developed for each type of welfare facility for disabled persons.