• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.638-646
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• 2018

The purpose of this study was to investigate the long-term habitat morphological alteration resulting from a large dam and weirs in the Tamjin River. To achieve this, we carried out a hydrograph analysis and a substrate size distribution analysis. We also estimated the channel width, bar area and vegetation encroachment using aerial photographs taken before and after the construction of the dam and weirs. The result of the hydrological analysis showed that flooding downstream was greatly reduced with small peaks occurrence after the dam construction. Interestingly, normal hydrographs in the main channel appeared just after tributary conjunction. There was a similar pattern in the substrate size analysis. Despite coarsened substrate just downstream of the dam site, more sand appeared again after introduction of the tributary. However, there was an increase in the bar area downstream of the dam's channels with most bars covered with vegetation. The channel width increased at the upper area of weirs through impoundment, but decreased downstream because of vegetation encroachment. This study indicate that unregulated tributary plays an important role in restoring hydro-physical habitat conditions in mainstream channels below a large dam. However, numerous weirs could be a causal factor to accelerate habitat deterioration in the dam downstream channels.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.541-552
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• 2018

The implementation of drought measures in the upstream areas of river basins is seldom considered with respect to water supply. However, the demand for such measures is increasing rapidly owing to the occurrence of severe droughts, and interventions on streams and the water supply are needed. Physical interventions are an option to prevent streams from becoming dry and to maintain stream water flow, but dam construction is challenging because of environmental and ecological considerations. Here, a feasibility study was conducted to assess the potential effects of sand dams, which are widely used in arid regions in Africa. The SWAT-K model, which is a hydrologic model used for Korean watersheds, is used to estimate the flow rate of water in an ungauged watershed. The changes in water storage of the sand-dammed reservoir and in downstream flow rates are estimated for two types of sand dam (natural and dredged). The results show that sand dams are capable of increasing the downstream flow rate during normal conditions and of mitigating water supply problems caused by the withdrawal of water during drought periods.

• The Korean Journal of Archival Studies
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• no.38
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• pp.3-35
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• 2013

The physical access or control of records with material entities is relatively easy. However, in the case of electronic records, due to its heightened applicative aspect that allows anyone with the authority to have access over the data, it requires an appropriate standard and stability to ensure the authenticity and integrity of electronic records. This study performed functional evaluation by extracting the minimum critical items from the national functional requirements documents and standards to explore the access control function that play an important role for the standard records management system to maintain quality requirements of electronic records. Based on this checklist, it evaluates whether the standard records management system properly carries out the access control function and investigates the current condition of application to practical records management work. Records managers generally do not use access control function, which may be because they do not feel the necessity, since the application of records management system is not yet actively promoted. In order for the standard records management system to be developed to become a more active system, it requires system improvement as well as considerations for below factors: First, although the necessity of establishing access control conditions is already recognized, it requires a clear stipulation of the regulation. Second, measures must be taken to implement access control in the records management system through document security solution. Third, it requires self-reflection of records manager, who utilizes the records management system. Instead of placing all responsibility on the National Archives, which established the system, professionals must further develop the system through continuous evaluation and improvement. Finally, a general discussion is required to publicize the issue of functional improvement of records management system. Although there is a bulletin board already created for this purpose, its users are extremely limited and it only deals with current problems. A space in online as well as in offline is required to solve the fundamental problems and exchange opinions.

• Journal of Adhesion and Interface
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• v.20 no.1
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• pp.1-8
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• 2019

Fabrication of monolayer is important method for enhancing physical and chemical characteristics such as light shielding and antireflection while maintaining thin film properties. In previous studies, monolayers were fabricated by various methods on small substrates, but processes were complicated and difficult to form monolayers with large area. We used rod coating equipment with a small amount of coating liquid to form a HCP (hexagonal closed packing) coating of PMMA beads on PET(poly(ethylene terephthalate)) substrate with $20cm{\times}20cm$ size. We observed that changes in morphologies of monolayers by using the solvents with different boiling points and vapor pressures, by adapting surfactants on particles and by applying plasma treatment on substrates. The coverage was increased by 20% by optimizing the coating conditions including meniscus of beads, control of the attraction - repulsion forces and surface energy. This result can potentially be applied to optical films and sensors because it is possible to make a uniform and large-scale monolayer in a simple and rapid manner when it is compared to the methods in previous studies.

• Journal of Korean society of Dental Hygiene
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• v.19 no.1
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• pp.55-64
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• 2019

Objectives: The purpose of this study was to compare the differences in oral health-related quality of life among elderly people aged over 65 years, in terms of physical, mental and oral health status and to analyze factors affecting their oral health-related quality of life. Methods: From May 9 to June 23, 2017, we randomly visited aged-care community centers in the metropolitan area, and recruited 222 elderly, aged 65 or older. First, each participant completed a questionnaire consisting of 4 general items: 1 systematic disease, and 3 subjective oral conditions. Afterwards, the researchers interviewed the participants to assess their mental status, using MMSE-DS and recorded the responses. Finally, an oral examination was performed to determine the number of remaining teeth. The average oral health-related quality of life according to each characteristic was analyzed by t-test and ANOVA. Hierarchical multiple regression analysis and Pearson's correlation coefficient analysis were used to analyze the correlations between factors and the factors affecting oral health-related quality of life. Results: The mean oral health-related quality of life was 4.15. Participants with 20 or more remaining teeth demonstrated better oral health-related quality of life than those with 19 or less teeth. Higher oral health-related quality of life was also found among elderly without gingival bleeding, self-reported halitosis and dry mouth. In addition, positive correlation with the number of remaining teeth and negative correlation with gingival bleeding, self-reported halitosis and dry mouth, were noted. Finally, the results of the hierarchical multiple regression analysis indicated that remaining teeth, gingival bleeding, self-reported halitosis and education were influential factors in determining the oral health-related quality of life among the elderly. Conclusions: The results of this study confirmed the necessity of better policy support, and the importance of implementing delivered, elderly-centered oral health education program by professionals to prevent tooth loss and manage periodontal diseases.

• Journal of the Korean Applied Science and Technology
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• v.38 no.2
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• pp.532-542
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• 2021

The purpose of this study was to investigate the body's strategy through kinematic variables of the lower extremities and ground reaction forces to maintain the club-head speed and ball accuracy despite the three stances during the golf swing. Ten male golfers who official handicap two were participate in the experiment. All subjects performed swing after maintaining the address posture according to stance conditions(square; SS, open: OS, closed: CS). Using a 3D motion analysis system and force plateform, the results were calculated with the 7-iron full swing each stance. In result, there was no difference in center of displacement, and left and right hip and knee joint angle displacement. Left ankle joint was largely plantar-flexed in OS, and right ankle joint was largely performed in CS from the address to the downswing. From address to take-back, right foot had a large left direction and the left foot had a right direction were greater in OS than in CS. Therefore, despite various stances, maintaining the same posture at impact is thought to have a positive effect on club head speed and ball direction.

• Journal of Industrial Convergence
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• v.19 no.1
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• pp.147-158
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• 2021

This study was conducted seven times from 2007 to the 2019 Women's World Handball Championships to analyze and strengthen the strength of the Korean women's handball team through the analysis of the top five countries' strengths. Among the 41 national teams participating in the World Women's Handball Championship, a total of five national teams, including the Netherlands, Norway, Russia, Spain, and France, were selected for the final study. Among the records provided by the International Handball Federation (IHF), the ranking was selected by analyzing the competition records of 41 participating countries, and technical statistics and frequency analysis were conducted using the SPSS/PC+ Ver21.0 program. based on the accumulated records of the top five women's handball competitions, handball attack and defense strategies that can make up for the inferiority in future physical conditions are needed and detailed follow-up studies are needed. Also, we hope to use it as a basic resource for improving the performance of Korean women's handball players and to play a key role in enhancing the level of women's handball at the 2021 Tokyo Olympics.

• Composites Research
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• v.33 no.6
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• pp.371-376
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• 2020

The adhesive strength can be improved through surface treatment. The most common method is to improve physical bonding by varying the surface conditions. This study presents the effect of laser surface treatment on the adhesive strength of CFRP. The surface roughness was patterned using a 1064 nm laser. The effects of the number of laser shots and the direction and length of the pattern on the adhesion of the CFRP/CFRP single joint were investigated through tensile tests. Tests according to ASTM D5868 were performed, and the bonding mechanism was determined by analyzing the damaged surface after a fracture. The optimized number of the laser shots and the optimized depth of the roughness should be required to increase the bonding strength on the CFRP surface. When considering the shear stress in the tensile direction, the roughness pattern in the direction of 45° that increases the length of the fracture path in the adhesive layer resulted in an increase of the adhesive strength. The surface treatment of the bonding surface using a laser is a suitable method to acquire a mechanical bonding mechanism and improve the bonding strength of the CFRP bonding joint. The study on the optimized laser process parameters is required for utilizing the benefits of laser surface processing.

• Journal of The Korean Association of Information Education
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• v.25 no.3
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• pp.557-569
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• 2021

In preparation for the future society, the educational curriculum is changing according to the trend of the times, and with the advent of the era of the 4th Industrial Revolution, the purpose of the new 2015 revised curriculum was suggested to foster the convergence creativity of students. The purpose of software education is to promote creativity and further develop problem-solving skills in connection with real life. In addition, flow in learning leads to outstanding educational achievement. However, in elementary school computer education, there is still a lack of development of a convergence class model for students to easily immerse themselves and promote creative problem-solving skills. Therefore, in this study, we designed convergence computer education using Novel Engineering, which is a convergence class model suitable for these educational conditions and applied it to classes. Further, to measure the effect on the improvement of learning flow and creative problem-solving ability. the Novel Engineering-based computer class was applied to the experimental group for 6th graders, and the general computer class was applied to the control group. As a result of the pre-post test between groups, it was found that computer classes using Novel Engineering had a positive effect on learning flow and creative problem-solving ability.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.395-399
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• 2011

Material of the gasket for lithium ion battery requires the chemical resistance, the electrical insulting property, the compression set, the anti-contamination level and the low temperature resistance. We compounded ethylene propylene diene monomer (EPDM), which showed widely different solubility parameter index, with adjusting the amount of metal oxide as an activator. We did long-term test and compression set against an electrolyte with consideration for operating conditions in lithium-ion battery. In these tests, we checked the physical, chemical characteristics and the effect to lithium ion battery with different kinds of activators. In case of rubber with ZnO as an activator, through 1000 h depositing test in propylene carbonate which is one of representative solvents, we could get the satisfying characteristics and result. However, $Zn^{2+}$ had eluted in the ion elution test. So, ZnO should be limited in EPDM compound for the gasket material in lithium-ion battery.