• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.4
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• pp.315-322
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• 2008

Valves in power plants are leaking internally by various damages including insertion of foreign objects on seat, seat crack, defects and fatigue crack of stem packing or welds etc. due to severe operating conditions such as high temperature and high pressure for extended period time. Acoustic emission(AE) technology should be applied in order to diagnose precisely and evaluate these valve internal leak. In this paper, results of studies which have accomplished in actual power plant are presented. We have analyzed background noise, AE signal level and frequency spectrum through laboratory tests on the basis of various actual conditions in power plant, and also have considered evaluation methods on the background noise, AE properties and the detectable minimum leak rate according to valve leak conditions through comparing with results of field tests in power plant. As a result of these studies, we conformed that evaluation of internal leak conditions including discrimination of leak or not, and the detectable minimum leak rate is possible, and also it is expected to contribute to safe operation and prevention of energy loss in power plants.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.296-302
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• 2019

In this study, a basic durability assessment was performed by selecting the main part of a trial product of a shale shaker, which is one of components for a mud circular system. For a preliminary durability assessment, it was assumed that the lifetime of the bearing for the vibrator motor and the stiffness of the support spring are affected by the vibration when the motor operates continuously. In the case of the motor, the initial p-p level was 0.72 g, but after 100 hours of operation, the p-p level was rapidly increased to 1.26 g. Bearing defects could be estimated through ball defect frequency analysis. In the case of the spring, the stiffness of the spring was reduced by approximately 3.78% at the end of 2,000 hours of the fatigue-durability test by applying excitation conditions to shale shaker body. In the future, we will analyze the influence of the particle removal efficiency of the shale shaker.

• Smart Structures and Systems
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• v.23 no.3
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• pp.263-278
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• 2019

Moving train load parameters, including train speed, axle spacing, gross train weight and axle weights, are identified based on strain-monitoring data. In this paper, according to influence line theory, the classic moving force identification method is enhanced to handle time-varying velocity of the train. First, the moments that the axles move through a set of fixed points are identified from a series of pulses extracted from the second derivative of the structural strain response. Subsequently, the train speed and axle spacing are identified. In addition, based on the fact that the integral area of the structural strain response is a constant under a unit force at a unit speed, the gross train weight can be obtained from the integral area of the measured strain response. Meanwhile, the corrected second derivative peak values, in which the effect of time-varying velocity is eliminated, are selected to distribute the gross train weight. Hence the axle weights could be identified. Afterwards, numerical simulations are employed to verify the proposed method and investigate the effect of the sampling frequency on the identification accuracy. Eventually, the method is verified using the real-time strain data of a continuous steel truss railway bridge. Results show that train speed, axle spacing and gross train weight can be accurately identified in the time domain. However, only the approximate values of the axle weights could be obtained with the updated method. The identified results can provide reliable reference for determining fatigue deterioration and predicting the remaining service life of railway bridges.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.2
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• pp.143-149
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• 2022

PCS needs to freely switch AC and DC to connect the battery, external AC loads and renewable energy in both directions for energy efficiency. Whenever converting happens, power loss inevitably occurs. Minimization of the power loss to save electricity and convert it for usage is a very critical function in PCS. PCS plays an important role in the ESS(Energy Storage System) but the importance of stabilizing semiconductors on PCB(Printed Circuit Board) should be empathized with a risk of failure such as a fire explosion. In this study, the temperature variation inside PCS was reviewed by cooling fan on top of PCS, and the vibration characteristics of PCS were analyzed during truck transportation for reliability of the product. In most cases, a cooling fan is mounted to control the inner temperature at the upper part of the PCS and components generating the heat placed on the internal aluminum cooling plate to apply the primary cooling and the secondary cooling system with inlet fans for the external air. Results of CFD showed slightly lack of circulating capacity but simulated temperatures were durable for components. The resonance points of PCS were various due to the complexity of components. Although they were less than 40 Hz which mostly occurs breakage, it was analyzed that the vibration displacement in the resonance frequency band was very insufficient. As a result of random-vibration simulation, the lower part was analyzed as the stress-concentrated point but no breakage was shown. The steel sheet could be stable for now, but for long-term domestic transportation, structural coupling may occur due to accumulation of fatigue strength. After the test completed, output voltage of the product had lost so that extra packaging such as bubble wrap should be considered.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.4
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• pp.189-198
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• 2023

Purpose: This study aims to investigate the preferences of hot spring users regarding the utilization of Asan's hot springs after the COVID-19 pandemic. Methods: A survey was conducted on 340 hot spring users visiting hot spring resorts in the Onyang, Dogo, and Asan hot spring districts. The survey was conducted twice from November 5th to November 7th, 2021, and from May 25th to 26th, 2022. The survey included general questions, such as the frequency of hot spring usage, the purpose of visits, and the intention for future visits. Specific questions were related to Asan hot springs, focusing on the reasons for choosing Asan, its perceived advantages, and improvement suggestions. Results: The survey revealed that the average number of visits to hot springs was less than five in the past five years, and the main reason for visiting was to recover from fatigue. A percentage of respondents said they would use hot springs more often when the COVID-19 pandemic ends. When asked about their reasons for visiting Asan hot springs, responses varied by age. However, across all groups, the majority considered "good water" as an advantage of Asan hot springs, while improvements to "hot spring facilities" was the highest response among all age groups. Thus, despite the decline in the number of customers due to COVID-19, the overall perception of hot springs remains positive. This suggests a promising future for the hot spring industry, with the potential for a return to pre-pandemic usage levels. Conclusion: These results provide valuable foundational data for informing policy development aimed at revitalizing the hot spring industry in the post-COVID-19 era.

• The Journal of Internal Korean Medicine
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• v.45 no.4
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• pp.591-601
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• 2024

Objectives: This study aimed to investigate the relationship between allergic diseases and digestive discomfort symptoms using a dataset for the traditional Korean medicine examination. Methods: The study included 389 subjects in the allergy group, diagnosed with allergic diseases by either a Korean medicine doctor or modern medical doctor, and there were 4,160 subjects in the control group. Propensity score matching was used to control the factors affecting the allergic disease and digestive discomfort symptoms. These factors included age, sex, medication history, obesity, smoking status, alcohol consumption, meal frequency, meal quantity, eating speed, sleep quality, stress level, and physical activity, matched at a ratio of 1:1. Logistic regression was used to estimate the adjusted odds ratio of digestive discomfort symptoms in the allergy group compared to the control group. Results: Compared to the control group, subjects in the allergy group had a significantly higher risk of having abdominal distention 1.62 times (OR=1.62, 95% CI: 1.13-2.32, p-value=0.008) and postprandial fatigue 1.41 times (OR=1.41, 95% CI: 1.02-1.95, p-value=0.037). Conclusion: The study suggests that allergic diseases were associated with certain digestive discomfort symptoms. The findings of this study can serve as a basis for managing both allergic diseases and digestive discomfort symptoms together.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.1293-1293
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• 2024

Virtual reality (VR) is increasingly utilized in the construction industry for diverse applications. Immersive virtual reality (IVR) offers practical experiences and educational opportunities for workers, enhancing productivity and safety. Efforts to optimize IVR involve analyzing biometric responses to monitor concentration, assess learning efficiency, and deliver personalized content. However, IVR faces challenges such as high production costs and prolonged production periods. Additionally, integrating biometric response recording into IVR experiences requires separate modules, further extending production timelines. To address these challenges, an integrated platform is necessary to streamline IVR production, user experience, and biometric response setup and recording. This study introduces such a platform designed to enhance the efficacy of IVR experiences through real-time biometric response analysis. The proposed platform comprises three main processes: (i) IVR content production using Unity; (ii) biometric response definition; and (iii) IVR content experience accompanied by generated logs for biometric responses. Firstly, IVR content production using Unity involves the development of IVR environments and scenarios. The platform incorporates diverse 3D models, including urban landscapes, building elements, and furniture, as the basis for IVR environments. Scenarios are constructed by integrating events into these environments, triggered by conditions such as reaching specific locations, the passage of time, or user interactions. Upon event activation, participants are presented with description UIs, quiz UIs, or route guidance, facilitating engagement and progression through interaction. Secondly, biometric responses encompass eye tracking and EEG. Eye tracking captures pupil diameter and fixation status on Areas of Interest (AOI), defined during IVR content production. EEG recording options include signals from each channel by default, as well as frequency-specific signals and EEG metrics such as attention, stress, fatigue, valence, and arousal. The platform supports the addition of new EEG metrics, enhancing customization and recording capabilities. Lastly, IVR content can be experienced alongside generated logs for biometric responses. The dataset enables monitoring and evaluation of participants' learning performance during IVR experiences, with the potential to enhance worker safety and productivity through immersive practical training and education.

• The Journal of Pediatrics of Korean Medicine
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• v.14 no.2
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• pp.149-168
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• 2000

The Purpose of this study was to investigate the new effective oriential medicine tretments in pediatric disease and its clinical applicability The study was composed of 1245 new patients who had been treated at the all unit in the Dong-Seo oriential Medicine Hospitial for 1 year, from 1 April 1999 to 31 March 2000, and aged between 0 and 18 years. The chief complaint was mainly categorized by oral examination on patients and their care-givers. Result 1. The numbers of children who involved in this study is total 1245: Male children are 668 and female children are 577 children. The sex rate between male and female is 1.15 to 1. 2. Most of the above patients came to the hospital at first time from diseases such as musculoskelectal disease, weakness, asthma, cough, anorexia, common cold, rhiorrhea, sweating, dyspepsia, dematitis, night terror, obesity, stomach, short stature, Besides, they also came to the hospital at first time from various diseases such as epistasxis, pyrexia. Bell's palsy, nocturia, contipation, cerebral palsy, disorder, CVA. diarrhea. stress disease, Allergic disease, Tic disorder. Visual disorder, Kawasaki disease, Pierre Robin's syndrom, hematuria, edema and so on. 3. Looking at the frequent diseases, Respiratory dis. children including asthma, cough, rhiorrhea, sweating, common cold, pyrexia covers 36%, in 399 numbers. digestive dis. children including anorexia, dyspepsia, stomach, diarrhea, constipation, indigestion covers 19%, in 211 numbers. cadiovasculary disease children including arrthymia, terror in frequency, night crying, sediation, Tic disorder covers 8%, in 85 numbers. Hepatobiliary disease children including short stature, dizziness, visual difficulty, sprain, disorder of nail covers 21%, in 238 numbers. renal disease. children including nocturia, hematuria, hemation, disorder of hair, menorrhea, cerebral palsy, edema in 44 numbers. Fatigue children covers 13%. in 143 numbers. 4. In case of respatory disease children. total number is 399 children. dematitis children are 108 numbers and asthma children are 96 numbers. These show that children seem to the best have dematitis and asththma. The age from 0 to 6 is 290 numbers, covering 73 percentage. The others are covering 27 percentage. These data demonstrate that the age from 0 to 6 age could easily get these kinds - of diseases. The 29 percent of children had these kinds of diseases in spring. The 28 percent of children had these kinds of diseases in autumn. These show that children seem to frequently have these kinds of diseases in both spring and autumn season.(inter-season) 5. In case of digestive disease, anorexia covers 39%, in 83 numbers, dyspepsia covers 28%, in 59 numbers, anorexia and dyspepsia were the lagest group in digestive disease and the age from 0 to 6 covers 59%, in 125 numbers and the other age covers 39%. According to these data, infant seems to be vulnerable to these kinds of diseases. The 24 percent of children had these kinds of diseases in spring and summer. The 33 percent of children had these kinds of diseases in winter, which means that children mostly had winter. but decreased significant in autumn. 6. In case of cadiovasculary diseases, it can be divided into two categories: night covers 73% and nervous characteristics covers 27%. The age from 0 to 6 occupies 75%, and the other age occupies 25%. These data also show that infants can easily infected with these kinds of diseases. Analyzing by the season, summer could be the most frequent season that children have these kinds of diseases. but decreased in autumn. 7. In case of hepatobiliary children, sprains covers 166 numbers, fatigue covers 32 numbers, epistasxia covers 24 members, the reasion which sprain occupyied most of % were sprain covered ages. The age from 0 to 14 covers 59% and from 15 to 18 covers 41%. In the conclusion the adolescent seems to be vulnerable to sprains. In spring 29%, insummer 31%, in autumn 23%, and in winter 28% of children got these kinds of diseases, which show that children seems to have this kinds of disease in summer season. and decreased in autumn. 8. In case of renal disease. nocturia and hematuria covers 52%(occupied overhalf). The age from 0 to 6 covers 52%(occupied overhalf). Analyzing by season, in spring increased in summer(59%), decreased in autumn(45%) Conclusion 1. The chief complant in pediatric diseases that needed an oriental medical tretment was mainly the disease that tends to take iong time and the weakness. and appeared frequency in respiratory disease : 2. The oriential medical tretment was still preferred as a way to improve the weakness by patients, rather than a way to overcome their disease. In paticular, the study shows that the oriental medical tretment should be emphasized in terms of preventing the disease 3, The new disease, which were developed with the change of human life and envir oment(just like seual disorder, short stature, obesity, dynamic disorder, examinee disease), should be in vestigated as a new field of oriental medical tretment.

• The Journal of Korean Society for School & Community Health Education
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• v.25 no.2
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• pp.27-44
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• 2024

Objectives: This study aimed to provide foundational data for preventing adolescents smoking by analyzing the relationship between adolescents' lifestyles and smoking experiences and identifying influencing factors. Methods: Secondary data analysis was conducted using the 17th (2021) Youth Health Behavior Survey data, encompassing 54,848 students from 796 schools. Variables included general characteristics, smoking status, lifestyle habits, physical activity, sleep patterns, and stress perception. Frequency analysis was used to examine general characteristics, while further analysis employed frequency analysis and the Pearson Chi-square test to compare lifestyle differences based on smoking presence. Multinomial logistic regression analysis was employed to determine factors influencing smoking experience, with IBM SPSS Statistics 28 used for all analyses at a significance level of p<.05. Results: Analysis revealed with general characteristics that the group with smoking experience exhibited a higher proportion of male students (67.4%) compared to the non-smoking group (50.1%) (p<.001). Analysis revealed that the smoking group was more likely to skip breakfast (27.7%), not consume fruit (17.8%), and consume fast food more than three times daily (0.9%). Furthermore, a higher percentage of smokers engaged in 60 minutes or more of breathless physical activity (8.4%) seven times a week, reported insufficient fatigue recovery through sleep (21.6%), and experienced very severe normal stress (17.2%) (p<.001). Analysis of the relationship between lifestyle and smoking indicated increased likelihood of smoking with zero breakfast consumption (OR=1.759, p<.001) and increased fruit consumption (OR=1.921, p<.001), while zero fast food consumption decreased smoking likelihood (OR=0.206, p<.001). Adequate sleep-related fatigue recovery reduced smoking likelihood (OR=0.458, p<.001), whereas increased stress elevated it (OR=1.260, p<.05). Conclusion: Adolescents' lifestyle habits significantly correlated with their smoking experiences, highlighting the necessity of considering lifestyle factors in smoking prevention strategies. This study provides crucial insights for promoting healthy lifestyle changes to prevent smoking among youth.

• Korean Journal of Psychosomatic Medicine
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• v.21 no.1
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• pp.44-54
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• 2013

Objectives : To investigate the frequency and clinical characteristics of premenstrual syndrome(PMS)/premenstrual dysphoric disorder(PMDD) in high school students, and determine the correlates of PMS/PMDD in association with comorbid depression and anxiety. Methods : A total of 1688 students were recruited from 5 high schools in Seoul, Korea. Subjects completed the questionnaire composed of scales to measure premenstrual symptoms, depression, and anxiety, as well as sociodemographic and reproductive variables. Subjects were categorized into 3 groups by using the Premenstrual Symptom Screening Tool(PSST) to determine the frequency and clinical characteristics of PMS/PMDD. Multivariate logistic regression was used to identify the correlates of PMS/PMDD. Results : The frequency of moderate to severe PMS and PMDD was 20.1% and 6.4%, respectively. Irritability(78.8%), fatigue(76.4%), and emotional sensitivity(69.8%) were common premenstrual symptoms, and functional impairment in academic performance(67.1%) was dominant. Dysmenorrhea[odd ratio(OR)=3.68, 95% confidence interval(CI) 2.45-5.55], family history of PMS(OR=1.91, 95% CI 1.35-2.71), and use of oral contraceptive (OR=1.85, 95% CI 1.16-2.94) were associated with the increased risk of PMS/PMDD after adjustment for depression and anxiety. Negative attitude to menses(OR=15.60, 95% CI 3.61-67.42) was associated with the increased risk of PMS/PMDD, particularly in subjects without depression and anxiety. Conclusions : PMS was common, as the frequency of PMS more than moderate severity including PMDD exceeded 25%, and disrupted daily functioning in adolescents. PMS is associated with various sociodemographic and menstrual characteristics, and these associations are affected by comorbid depression and anxiety.