• Journal of the Korean Society of Safety
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• v.35 no.1
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• pp.107-115
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• 2020

This paper introduces the first vital area identification (VAI) process for the physical protection of nuclear power plants (NPPs) during low power and shutdown (LPSD) operation. This LPSD VAI is based on the 3rd generation VAI method which very efficiently utilizes probabilistic safety assessment (PSA) event trees (ETs). This LPSD VAI process was implemented to the virtual NPP during LPSD operation in this study. Korea Atomic Energy Research Institute (KAERI) had developed the 2nd generation full power VAI method that utilizes whole internal and external (fire and flooding) PSA results of NPPs during full power operation. In order to minimize the huge burden of the 2nd generation full power VAI method, the 3rd generation full power VAI method was developed, which utilizes ETs and minimal PSA fault trees instead of using the whole PSA fault tree. In the 3rd generation full power VAI method, (1) PSA ETs are analyzed, (2) minimal mitigation systems for avoiding core damage are selected from ETs by calculating system-level target sets and prevention sets, (3) relatively small sabotage fault tree that has the systems in the shortest system-level prevention set is composed, (4) room-level target sets and prevention sets are calculated from this small sabotage fault tree, and (5) the rooms in the shortest prevention set are defined as vital areas that should be protected. Currently, the 3rd generation full power VAI method is being employed for the VAI of Korean NPPs. This study is the first development and application of the 3rd generation VAI method to the LPSD VAI of NPP. For the LPSD VAI, (1) many LPSD ETs are classified into a few representative LPSD ETs based on the functional similarity of accident scenarios, (2) a few representative LPSD ETs are simplified with some VAI rules, and then (3) the 3rd generation VAI is performed as mentioned in the previous paragraph. It is well known that the shortest room-level prevention sets that are calculated by the 2nd and 3rd generation VAI methods are identical.

• The Journal of Korean Society for School & Community Health Education
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• v.14 no.2
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• pp.1-14
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• 2013

Objectives: The purpose of this study was to identify the relationship of internet use time and health risk behaviors among adolescents and provide data to set up a strategy for preventing internet addiction. Methods: The data of the 2011 Youth Health Risk Behavior web-based Survey Collected by Korean Center for Disease Control was analyzed using t-test, ANOVA, Chi-square test for this study. Results: There were significant differences between boys and girls in internet use time. Boy's internet use time was different according to city size(F=13.20, p<.001), grade(F=35.85, p<.001), school record(F=298.95, p<.001), economic state(F=326.75, p<.001), living with parents(t=11.60, p<.001), father's education level(F=147.92, p<.001), and mother's education level(F=110.93, p<.001). Girls' internet use time was also different according to school grade(t=-8.68, p<.001), grade(F=61.03, p<.001), school record(F=233.32, p<.001), economic state(F=185.78, p<.001), living with parents(t=10.81, p<.001), father's education level(F=86.54, p<.001), and mother's education level(F=92.64, p<.001). Regarding the health risk behaviors, present smoking, present alcohol drink, drug use skipping breakfast, eating fast food, drinking soda, sexual behavior, suicidal attempt, engagement time in physical education classes, severe exercise, and sleeping satisfaction made differences in the internet use time. Conclusions: The results suggest that health risk behaviors are influenced by internet use time of adolescents. Thus, these results may be contribute to development of programs to prevent internet addiction.

• Journal of Korean society of Dental Hygiene
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• v.13 no.6
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• pp.917-923
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• 2013

Objectives : The purpose of this study was to investigate the level of expertise and awareness of information on toothpaste in dental hygienists and to give patients information on toothpaste. Methods : The subjects was 205 dental hygienists working at dental clinic, dental hospital or college dental hospital in Seoul and Gyeonggi-do. They filled out the questionaire from 13th to 27th April, 2013. Collected data were analyzed by SPSS 21.0 program and significant level was set at p=0.05. Results : The awareness of information on toothpaste was the highest in dental hygienists having under 3 years career and working at dental clinics(p<0.001). The level of expertise on toothpaste was the highest in those having over 5 years career and working at general hospital or college dental hospital(p<0.001). In association with the effect of toothpaste(p<0.05), experienced dental hygienists had a higher knowledge(1.68 point) that those who had no experience(2.27 point). Instruction of the oral care devices included 27.5% of dental floss, 27.1% of toothbrush and 25.4% of proxabrush, and 4.9% of toothpaste. Conclusions : The results revealed that the right choice of the toothpaste would be the best prevention of dental caries and it is necessary to educate the dental hygienists for the toothpaste information.

• The Journal of Korean Physical Therapy
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• v.22 no.6
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• pp.77-83
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• 2010

Purpose: The aim of this study was to do numerical analysis of the wavelength dependence in low level laser therapy (LLLT) using a finite element method (FEM). Methods: Numerical analysis of heat transfer based on a Pennes' bioheat equation was performed to assess the wavelength dependence of effects of LLLT in a single layer and in multilayered tissue that consists of skin, fat and muscle. The three different wavelengths selected, 660 nm, 830 nm and 980 nm, were ones that are frequently used in clinic settings for the therapy of musculoskeletal disorders. Laser parameters were set to the power density of 35.7 W/$cm^2$, a spot diameter of 0.06 cm, and a laser exposure time of 50 seconds for all wavelengths. Results: Temperature changes in tissue based on a heat transfer equation using a finite element method were simulated and were dominantly dependent upon the absorption coefficient of each tissue layer. In the analysis of a single tissue layer, heat generation by fixed laser exposure at each wavelength had a similar pattern for increasing temperature in both skin and fat (980 nm > 660 nm > 830 nm), but in the muscle layer 660nm generated the most heat (660 nm ${\gg}$ 980 nm > 830 nm). The heat generation in multilayered tissue versus penetration depth was shown that the temperature of 660 nm wavelength was higher than those of 830 nm and 980 nm Conclusion: Numerical analysis of heat transfer versus penetration depth using a finite element method showed that the greatest amount of heat generation is seen in multilayered tissue at = 660 nm. Numerical analysis of heat transfer may help lend insight into thermal events occurring inside tissue layers during low level laser therapy.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06b
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• pp.215-225
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• 2006

Today's requirements for print-press runnability and print quality demand an optimised absorption and adhesion of printing ink on the paper surface. Modern coating concepts for high glossing offset grades use ultra fine pigments, whereas binder level has continuously been decreased to a minimum in recent years to achieve the highest possible sheet gloss development and for economical reasons. Both the ultra fine pigments and the reduced binder levels lead in many cases to a faster ink setting rate. On the other hand, matt paper grades use relatively coarse pigments leading to a slow ink setting compared to the high glossing papers. Both too fast and too slow ink setting properties implicate drawbacks in print quality and print press runnability. The mechanisms behind the interactions between ink and coating have been presented in many previous publications. The purpose of this study was to determine and quantify how the ink setting rate is influenced by pigment system (GCC and GCC/clay blends), latex level and latex properties in the topcoat of double coated sheet fed offset paper. The roles of binder level and type in the precoat were also assessed. The effect of calendering (temperature and pressure) was studied with one formulation. The resulting ink setting characteristics were tested using three different laboratory testing instruments. The correlation amongst the different laboratory testing methods is discussed. The results show that by varying the latex properties, the pigment system and/or latex addition level, the ink tack development of ink applied to a topcoat pigment system can be significantly influenced. It can be slowed down as often desired with ultra fine pigments or speeded up in the case of coarse pigments. There was no visible effect on the ink setting rate by using different binder systems in the precoat..

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.159-167
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• 2015

We consider a wafer lot transfer/release planning problem from semiconductor wafer fabrication facilities to probing facilities with the objective of minimizing the deviation of workload and total tardiness of customers' orders. Due to the complexity of the considered problem, we propose a two-level hierarchical production planning method for the lot transfer problem between two parallel facilities to obtain an executable production plan and schedule. In the higher level, the solution for the reduced mathematical model with Lagrangian relaxation method can be regarded as a coarse good lot transfer/release plan with daily time bucket, and discrete-event simulation is performed to obtain detailed lot processing schedules at the machines with a priority-rule-based scheduling method and the lot transfer/release plan is evaluated in the lower level. To evaluate the performance of the suggested planning method, we provide computational tests on the problems obtained from a set of real data and additional test scenarios in which the several levels of variations are added in the customers' demands. Results of computational tests showed that the proposed lot transfer/planning architecture generates executable plans within acceptable computational time in the real factories and the total tardiness of orders can be reduced more effectively by using more sophisticated lot transfer methods, such as considering the due date and ready times of lots associated the same order with the mathematical formulation. The proposed method may be implemented for the problem of job assignment in back-end process such as the assignment of chips to be tested from assembly facilities to final test facilities. Also, the proposed method can be improved by considering the sequence dependent setup in the probing facilities.

• The Journal of Internal Korean Medicine
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• v.42 no.4
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• pp.672-686
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• 2021

Objectives: The purpose of this study is to assess the efficacy and safety of Baekhogainsam-tang for type 2 diabetes without complications by systemic review and meta-analysis of randomized controlled trials (RCTs). Methods: For a systematic review and meta-analysis, we set a key question in accordance with PICOT-SD. We searched the following up to March 31. 2021: PubMed, EMBASE, The Cochrane Library, CNKI, CiNii, KISS, KMBASE, OASIS, and ScienceON. A meta-analysis was conducted by synthesizing the results, including fasting plasma glucose level, postprandial 2-hour plasma glucose level, and Glycated Hemoglobin (HbA1c). Results: A total of five trials are included in this systemic review. The treatment group (Baekhogainsam-tang plus conventional treatment) showed more statistically significant effect than did the control group (conventional treatment only) in fasting plasma glucose level, postprandial 2-hour plasma glucose level, and glycated hemoglobin (HbA1c). Conclusions: Baekhogainsam-tang showed statistically significant effects in hypoglycemic effect and in improving insulin resistance. However, the number of studies included in the meta-analysis was insufficient, and the BIT used in the included studies was not standardized. This topic requires further attention and more clinical research.

• Journal of Korean society of Dental Hygiene
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• v.23 no.2
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• pp.125-132
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• 2023

Objectives: This study used the 2018 Korea Health Panel Survey data to analyze factors affecting employment status and income relating to unmet dental and medical care needs. Additionally it investigated measures to reduce oral health inequality among various socioeconomic classes. Methods: Descriptive statistics for the subjects' unmet dental and medical care needs were calculated through chi-square test analysis, and multivariate logistic regression analysis was applied to identify factors affecting the unmet dental and medical care needs. The odds ratio and 95% confidence interval were calculated for each level. These data were analyzed using STATA 17.0 SE (64-bit) version, and the statistical significance level was set to p<0.05. Results: As a result of unmet dental and medical care needs according to general characteristics, the lower the education level (p<0.001), the higher the age (p<0.001) and the lower the household equalization income (p<0.024) and the smoker status (p<0.003) were, respectively. Factors that have a statistically significant impact on unmet dental and medical care needs were divorce, separation and bereavement (p<0.001) in individuals than in married persons, and being smokers than non-smokers (p<0.009). The frequency of unmet dental and medical care needs were found to be lower in the cases of a high school graduate than an elementary school graduate (p<0.018), and of higher household equalization income (p<0.001) than the lowest household equalization income, respectively. Conclusions: It was found that various factors such as age, education level, household equalization income, employment status, type of working hours type, and smoking status affect unmet dental and medical care needs.

• Restorative Dentistry and Endodontics
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• v.47 no.3
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• pp.33.1-33.10
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• 2022

Objectives: This study aimed to analyze the proximity of maxillary molar roots to their overlying cortical bone surfaces and the maxillary sinus. Materials and Methods: Cone-beam computed tomographic images of 151 patients with completely erupted upper molars that had 3 separate roots were studied. The following distances were measured: from the root apex to the cortical plate and maxillary sinus floor, and from the apical 3-mm level of the root to the cortical plate. Differences between groups were analyzed with 1-way analysis of variance and the Scheffé post hoc test, the significance of differences between cone-beam computed tomography views with the paired t-test, and the significance of differences among age groups with linear regression analysis. The significance level was set at p < 0.05. Results: The mesiobuccal and distobuccal root apexes of maxillary second molars were more distant from the buccal cortical plate than the maxillary first molars (p < 0.05). The apical 3-mm level of the mesiobuccal root of the first molar was closer to the buccal cortical bone than the second molar (p < 0.05). In the maxillary first molars, the thickness of the buccal cortical bone decreased in all roots with age (p < 0.05). In all root apexes of both molars, the difference in the vertical level between the maxillary sinus floor and the root apex increased with age (p < 0.05). Conclusions: Awareness of the anatomical profile of maxillary molar apices in relation to the cortical bones and maxillary sinus will be beneficial for apical surgery.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.4
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• pp.385-394
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• 2023

Objectives: Firefighters could be exposed to a range of toxic chemicals during firefighting. When tyre burns, various toxic chemicals including volatile organic compounds(VOCs) could be emitted. In this study, the researchers assessed the VOC exposure of firefighters during tyre fire suppression through biomonitoring. Methods: There was a big tyre fire on 12 March 2023. Of the responding firefighters, we recruited 14 participants to collect their urine after firefighting. One week later, researchers collected firefighters' urine again right after their off-duty period. We analyzed each metabolite of benzene, toluene, xylene, and styrene in urine and compared their exposure level based on sampling time. Results: The detection rate for metabolite of benzene, toluene, styrene, and xylene in urine sampled at each time was 43%-64%, 100%, 86%-100%, and 100%, respectively. Except for the benzene, metabolite levels measured in urine after firefighting were similar to that from off-duty period. However, the median concentration of benzene metabolite in urine sampled after firefighting was three times higher compared to that from off-duty period(34.2 ㎍/g crea. and 10.9 ㎍/g crea., respectively.) The estimated airborne concentration of benzene calculated from metabolite level in urine was 0.16 ppm, which exceeded the recommended exposure level set by the National Institute for Occupational Safety and Health. Conclusions: This study shows that firefighters could be exposed to the high level of VOCs including benzene during their firefighting especially at tyre fire. These results could be used as a valuable data to prove firefighters' exposure to hazardous chemicals during their duty.