• Journal of Korean Society for Quality Management
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• v.31 no.3
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• pp.193-204
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• 2003

In this paper, we consider a periodic preventive maintenance(PM) policy in which each PM reduces the hazard rate but remains the pattern of hazard rate unchanged. And the system undergoes only minimal repairs at failures between PM's. The expected cost rate per unit time is obtained. The optimal number N of PM and the optimal period x, which minimize the expected cost rate per unit time are discussed. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.557-564
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• 2009

Welding residual stress is occurred after welding process. Tensile residual stress is one factor of PWSCC. Repair welding usually happened during the manufacturing welding process. Repair welds cause strong tensile residual stress. In PWR, Repair weldments made by Alloy 82/182 is susceptible to PWSCC caused by tensile stress, material and environment. Therefore, mitigation of welding residual stress in weldments is important for reliable operating. PWOL is one of the methods for mitigation and verified for over twenty years. In this paper, residual stress distribution of repaired weldments and the effect of PWOL on mitigation is examined for surge nozzle.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.148-149
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• 2022

본 논문에서는 지역별로 발생 양상이 다른 사회재난의 종합적 위험분석을 위한 정보활용 방안 및 전략을 제안한다. 사회재난은 재난유형이 매우 다양하며, 각기 다른 발생 및 전파양상을 가지고 있어 전문성을 기반으로 관계하고 있는 개별부처에서 각각 관리되고 있다. 재난이 발생 후 대응, 수습 및 복구에 이르는 활동은 대표적인 현장대응 부처인 행정안전부, 경찰청, 소방청 등에서 주로 담당하고 있으나, 예방 및 대비 활동은 각 부처에서 개별법령에 의한 제도 및 정책에 의해 위험요소를 저감하기 위한 활동으로 진행된다. 예를 들어 화학사고의 경우 화학사고예방관리계획서, 장외영향평가, 화재는 방화지구, 화재경계지구, 산불은 산불취약지수 등 각각의 물리적 매커니즘을 적정히 고려하는 이론적 근거의 의해 사전에 그 위험을 평가하고 있으나 재난관리 예방을 담당하는 부처에 까지 연속성을 가지고 그 결과들이 적극적으로 활용되고 있지 못하고 있다. 이에 본 연구에서는 각 부처에서 개별법령에 의해 평가되는 공신력 있는 자료들의 융합적 해석에 근거한 종합위험 평가 개념을 정립하고 실제 활용 가능성에 대해 논하고자 한다.

• Journal of Digital Convergence
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• v.12 no.4
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• pp.367-378
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• 2014

The purpose of this study was to explore the factors related to internet addiction in college student of Korea. Methods: From November 19, 2012 until December 14, 2012, 300 college students from one of the universities located at K city were surveyed. This study is a cross-sectional survey of college students in K city, and data was collected through self-report questionnaires. Data was analyzed by Fisher's exact test, independent t-test to identify different according to addiction group, and logistic regression analysis in order to factors related to on health behavior, sexual behavior and mental health of among college students. According to results, factors related to risk of addiction were lower frequency of exercise (p<0.05), no eat breakfast for 2 day (p<0.05), porno magazine/porno video contact pornography (p<0.05), subjective happiness index (p<0.05), and suicidal Ideation (p<0.05). This study suggest that exercise, regular diet, important of reproductive health, subjective happiness index and Suicidal Ideation are associated with internet addiction in College student. It is necessary to develop some preventive programs for those of internet addiction.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.389-401
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• 2016

This study attempted to present the monthly distribution of the inshore gill netters for the prevention of propeller failure caused by the damage of fishing gear by the merchant vessels in the West Sea. This study was conducted using the transmitting device of fishing location (V-Pass) data for 1 year in 2014. The grid intervals are $30minute{\times}30minute$ ($latitude{\times}longitude$) based on the section of the sea. A total of 56 sections were analyzed by constructing a grid. The results revealed that the section no. 194 with the highest density index showed no fishing gear damage accident. But the section no. 193 with a relatively lower density index showed more frequent fishing gear damage accident. It is because the section no. 193 is included in the main route of the merchant vessels. Based on this analysis, it is found that the fishing gears are not damaged in proportion to density index but risk of damage exists according to the main routes of merchant vessels. Therefore, for the safe navigation of the merchant vessels, notifying the waters of $34.5^{\circ}{\sim}35.5^{\circ}$ at latitude and $125.67^{\circ}{\sim}126^{\circ}$ at longitude, as a navigational warning area from May through September, will prevent marine accident, such as propeller failure and fishing gear damage. Accordingly, when the merchant vessels navigate in the section no. 193 and 203, the area of $34.5^{\circ}{\sim}35.5^{\circ}$ at latitude and $125.5^{\circ}{\sim}125.67^{\circ}$ at longitude is recommended for the safe navigation.

• Journal of dental hygiene science
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• v.13 no.4
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• pp.418-425
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• 2013

This study was investigated in order to provide basic data for prevention of periodontal disease and maintenance through proper lifestyle by finding the relevance of periodontal health with lifestyle habits. Data were collected from total of 326 subjects in their forties and fifties by using questionnaire and examination of periodontal health status. Results were analyzed by using IBM SPSS Statistics 19.0. The smoking status were statistically significant to gingival index (p<0.01), pocket depth (p<0.001), and clinical attachment loss (p<0.001). Smoking amount per day were statistically significant to gingival index (p<0.05), pocket depth (p<0.01), and clinical attachment loss (p<0.001). Duration of smoking were statistically significant to gingival index (p<0.05), pocket depth (p<0.01), and clinical attachment loss (p<0.001). Drinking cycle were statistically significant to gingival index (p<0.05), and clinical attachment loss (p<0.05). It is investigated that smoking (p<0.05) influence on clinical attachment loss. Dental care institute needs to make patients be aware of the fact that excessive smoking and drinking affect the periodontal health status for prevention of periodontal disease and maintenance of oral health. Therefore systematic educational programs to stop smoking and drinking should be prepared.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5518-5524
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• 2011

The purpose of this study is to investigate the change of balance ability on aging by measuring balance ability of elderly females whose age is over 65. The subjects are ten elderly women (the mean age: 71.9) able to walk without assistants, the assistant equipments and drug dependence and ten young healthy women (the mean age: 23.2). We measured stability index (ST), Fourier index (F), weight distribution (WD), weight distribution index (WDI), synchronization index (SI) and fall index (FI) by using Tetrax (Tetra-ataxiometric Posturography). In result, STs and Fs at the low frequency region (F1) represented the significant difference between two groups at all postures with PO (pillow with eye open) exception (p<.01). Fs at the other frequency regions (F2~F8) represented the significant difference between two groups (p<.05). WDI of the elderly women represented the higher values than the young women at all postures but there are the significant difference at PO and PC (pillow with eye closed) only. These results may be due to age-related ability decline of somatesthesia, vestibular organ, central nervous system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4349-4358
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• 2013

This study aimed to examine the relation between subjective oral hygiene status of the elderly and oral health impact profile and to present it as basic data for the improvement of quality of life and oral care. The study subjects were 231 elderly people aged 65 and over. This study measured the oral health behavior and subjective oral hygiene status based on cross analysis by calculating the median of OHIP-14 to divide the above-median group into a subgroup and the below-median group into a superordinate group. Correlation and regression analyses were performed to examine the effects on the oral health impact profile. The oral health impact profile according to oral health behaviors was not significant. The oral health impact profile based on the subjective oral hygiene states is currently affected by oral hygiene status, masticatory problems, toothache, xerostomia and halitosis. As a result of regression analysis to confirm the effect on the oral health impact profile, much experience of masticatory problems, toothache, xerostomia and gum diseases is the most influential. This shows that the subjective oral hygiene status is not healthy as the oral health impact profile is high. It is considered necessary to establish an oral health promotion program to improve the quality of life of the elderly and active oral care methods in the future.

• Journal of the Korea Institute of Building Construction
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• v.19 no.4
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• pp.361-371
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• 2019

In 2017, the ratio of the number of victims and deaths in the construction industry was the highest with 25.2% and 29.6%, respectively. Especially, as safety accidents at construction sites continue to increase, the economic loss is greatly increased too. Therefore, in order to prevent safety accidents in the construction work, the safety risk assessment index by type of construction was developed, and the main results of this study are as follows. First, 17 factors related to safety accidents at construction sites were derived through survey and interview survey, and this study suggested 9 items(process, type of construction, progress rate, contract amount, number of floors, safety education, working days and weather) throughout the expert advisory meeting. Second, the risk assessment index for safety accidents was developed based on the ratio and intensity of safety accidents. Third, to verify the risk assessment model, the construction safety risk assessment index by type of construction was derived by surveying and analyzing the statistics of the construction accident. In addition, the risk strength was calculated by dividing human damage caused by construction safety accidents into those killed and injured. The risk assessment index based on the frequency and intensity of safety accidents by type of construction is expected to be utilized as basic data when assessing the risk of similar projects in the future.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.49 no.4
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• pp.349-354
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• 2023

Sunscreen is a product that protects against ultraviolet rays by blocking and scattering ultraviolet rays, and has now become a daily necessity beyond cosmetics. Applying sunscreen is a common and easy way to prevent skin damage caused by ultraviolet rays. Due to its significance, the evaluation of sunscreen has evolved since its regulation by the FDA in 1978, progressing to standardized methods established by ISO. Additionally, to assess the loss of sunscreen due to activities such as water exposure or sweating, the Ministry of Food and Drug Safety in Korea and ISO have established protocols for evaluating the water-resistant sun protection factor (SPF). However, existing evaluations of water resistance have been mainly confined to test methods involving plain water, and methods accounting for the impact of seawater during activities like beach leisure, sports, and recreation are yet to be established. Based on the existing guidelines for testing the water-resistant UV protection index, this study compared the water-resistant UV protection index in water, artificial seawater (salt water) and natural seawater (sea water) to evaluate the UV protection index in real-world situations such as marine leisure, sports, and leisure activities. Through these results, we were able to compare the differences between water resistance sun protection index tests in ordinary water, artificial seawater, and natural seawater, and suggest a method for water resistance sun protection index tests using natural seawater.