• International Journal of Highway Engineering
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• v.5 no.1 s.15
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• pp.1-10
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• 2003

The objective of pavement design, just as with the design of other structures, is to obtain the most economical designs at specified levels of reliability. Methods that yield designs with different levels of reliability are undesirable, and over the course of time design approaches in the U.S. and Europe have converged toward the Load and Resistance Factor Design (LRFD) format in order to assure uniform reliability. At present the LRFD format has been implemented in concrete, steel, wood and bridge design specifications. In this paper, reliability theories are used to illustrate the development of an LRFD format for Mechanistic-Empirical (M-E) design of flexible pavements as an alternative of its reliability module. It is shown in this paper that ten candidate pavement sections designed with a reliability level using the AASHTO design guide (1986) do not have uniform structural reliability in terms of pavement mechanistic distress such as fatigue cracking and the uniform reliability can be achieved by using the LRFD format.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.273-281
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• 2010

In this paper, a method to predict the fatigue life of an axle drive shaft by the calibrated accelerated life test (CALT) method is proposed. The CALT method is very effective for predicting lifetimes, significantly reducing test time, and quantifying reliability. The fatigue test is performed by considering two high stress and one low stress levels, and the lifetime at the normal stress level is predicted by extrapolation. In addition, in this study, the major reliability parameters such as the lifetime, accelerated power index, shape parameter, and scale parameter are determined by conducting various experiments. The lifetime prediction of the axle drive shaft is verified by comparing the experimental results with load spectrum data. The results confirm that the CALT method is effective for lifetime prediction and requires a short test time.

• Korean Journal of Health Education and Promotion
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• v.19 no.3
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• pp.121-133
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• 2002

The purpose of this study was to set up the basic model to monitor the health status of the middle and high school students in the adolescent period, as well as to provide the fundamental data which might serve as the new standards for their better health maintenance and promotion. The collected data comprised the characteristics of the subjects in the three different fields of life such as school, family and everyday, which could affect their physical fatigues, and they were analyzed to determine the factors of significant influence upon their physical fatigues and to reveal their relativity. A total of 5,954 students at 6 boys' and girls' middle and high schools in Taejon City completed self-administered questionnaires(to measure Health Practice Index and others) asking about each of three life domains during the period March through June, 2000. The key study results were as follows; 1. The middle school students showed more subjective symptoms of fatigue which may be a marker reflecting physical health status, than the high school students. The higher scores were associated, based on school life, with the groups who were boys, who were in lower school grades, who achieved better academic performances and had better relationship with friends. 2. As for family life, the higher scores were in the groups whose financial conditions were better, whose parents showed more interest to their children, whose sense of satisfaction with family life was higher, and whose health status was better. 3. As for life styles, the individuals showed the higher scores in the groups who had breakfasts daily, who didn't have inter-meal snacks, who took regular exercises, who didn't smoke and drink than, their counterparts. 4. The higher level of fatigue was associated with the groups whose health conditions were good, who are satisfied with school life, who were boys rather than girls, who are satisfied with family life, who didn't have inter-meal snacks, who were in good relationship with friends, who achieved greater academic performances, who took regular exercises, who didn't smoke, and whose parents showed more interest in their children.

• International Journal of Highway Engineering
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• v.1 no.2
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• pp.155-168
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• 1999

Asphalt pavement tends to rut in high temperature and to crack in cold temperature. The performance of asphalt pavement can be deteriorated by korean weather condition which has the four distinct seasons. In this study, the typical sections that may minimize rutting and fatigue were analyzed through the numerical model tests. The layered elastic theory , finite element method and visco elastic theory were utilized for these numerical model tests. From the various numerical model tests, it is found that an optimum design procedure was recommended. It was increasing the thickness of asphalt stabilized base with fixing the wearing course as 5cm the minimum specified thickness. The section was most beneficial in resting rutting and fatigue. From the analysis of the relative index on tensile strain and cost analysis, it was recommended that the thickness ratio of subbase and asphalt concrete is 1.0$\sim$2.5.

• Journal of the Korean Society of School Health
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• v.36 no.3
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• pp.113-125
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• 2023

Purpose: The purpose of this study is to develop a model for predicting mental health risk among adolescents based on health behavior information by employing a hybrid machine learning method. Methods: The study analyzed data of 51,850 domestic middle and high school students from 2022 Youth Health Behavior Survey conducted by the Korea Disease Control and Prevention Agency. Firstly, mental health risk levels (stress perception, suicidal thoughts, suicide attempts, suicide plans, experiences of sadness and despair, loneliness, and generalized anxiety disorder) were classified using the k-mean unsupervised learning technique. Secondly, demographic factors (family economic status, gender, age), academic performance, physical health (body mass index, moderate-intensity exercise, subjective health perception, oral health perception), daily life habits (sleep time, wake-up time, smartphone use time, difficulty recovering from fatigue), eating habits (consumption of high-caffeine drinks, sweet drinks, late-night snacks), violence victimization, and deviance (drinking, smoking experience) data were input to develop a random forest model predicting mental health risk, using logistic and XGBoosting. The model and its prediction performance were compared. Results: First, the subjects were classified into two mental health groups using k-mean unsupervised learning, with the high mental health risk group constituting 26.45% of the total sample (13,712 adolescents). This mental health risk group included most of the adolescents who had made suicide plans (95.1%) or attempted suicide (96.7%). Second, the predictive performance of the random forest model for classifying mental health risk groups significantly outperformed that of the reference model (AUC=.94). Predictors of high importance were 'difficulty recovering from daytime fatigue' and 'subjective health perception'. Conclusion: Based on an understanding of adolescent health behavior information, it is possible to predict the mental health risk levels of adolescents and make interventions in advance.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.2
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• pp.181-189
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• 2021

Purpose: The purpose of this study is to investigate the stress response and sleep state of the new patients who visit the hospital for prosthodontic treatment due to tooth loss to make reference to further treatment direction. Materials and methods: Examinations, consultations, and surveys were conducted on 236 patients (94 males, 142 females, and 24-86 years old), who newly registered at the department of prosthodontics at Pusan national university hospital, for 2 years from 2018. The number of remaining teeth, edentulous arch, possibility of mastication, and future prosthetic treatment directions were recorded. The visual analogue scale (VAS), stress response inventory (SRI) and Insomnia severity index (ISI) were used as tools to measure patient's subjective discomfort, stress response, and sleep status. Results: Among the entire prosthodontic patient group, the average value of 'fatigue' was significantly higher among the 7 items of SRI, and the value of 'aggression' was significantly lower (P<.001). There are a significant difference between the edentulous and full dentition in the oral discomfort value measured by VAS (P=.004). In cases where less than 20 teeth remain, mastication is impossible, and patients who are planning treatment with removable prostheses, VAS value and 'depression' and 'fatigue' values in SRI were higher than those in the reverse case (P<.05). The patients showed severe level in VAS value have high value of 'tension', 'somatization', 'depression', 'fatigue'and 'frustration'in SRI than non-serious patients (P<.05). Clinical insomnia occurred in 11.4% of all patients, and women had significantly lower sleep quality than men (P=.044). Patients with insomnia showed significantly higher scores on the VAS value and all 7 SRI items than those of normal sleepers (P<.05). Conclusion: The new prosthetics had high 'fatigue' value among the 7 items of SRI. The oral condition, number of residual teeth and mastication function and clinical insomnia affected oral discomfort and the stress response.

• Journal of Digital Convergence
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• v.16 no.6
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• pp.251-258
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• 2018

We study convergent factors to depression(CES-D: Center for Epidemiologic Studies Depression scale) among administrative staff in general hospital. The questionnaire was used using an unregistered self-administered questionnaire for 201 staff from 9 general hospitals located in J area from Jul. 3rd, 2017 to Jul. 29th, 2017. The hierarchical multiple regression analysis shows the following results. The depression of respondents turned out to be significantly higher in following groups: a group in which Rosenberg Self-Esteem Scale(RES) is lower, a group in which Multidimensional Fatigue Scale(MFS) is higher, a group in which Psychosocial Well-being Index Short Form(PWI-SF) are higher. The results show explanatory power of 32.5%. The results of the study indicate that the efforts, to increase RES, and to decrease MFS and PWI, are required to improve the depression among administrative staff in general hospital. These results could be used in organizing human resource management and industrial health education to lower the level of depression in general hospital administration staff. Following studies need to analyze the structural equation model that effects the depression levels of administrative staff in general hospital.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.109-116
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• 1988

The strength and load of structure are varied with the Passage of time, and become a process of probability. It is possible to estimate the reliability from the relation between strength and load. Considering the safety, It is reasonable to estimate allowable stress from the safety factor based on the reliability. In this study, the method to estimate probability of fracture, which is index of reliability for rail subjeict to long term fatigue load were examined. In estimation of reliablity it is meaningless to evaluate numerical value especially this difficult case estimating parameter of random variable. To overcome this problem, conventional design method estimating relative reliability were proposed. In this study the Cornell method were examined. The uncertainity of random variale, ie coefficient of variation which is the index of variation of strength and load were considered. The effect of uncertainity related to probability of fracture, and safety factor based on reliability were examined. The results of this study are followed. The reliability of weld metal were influenced by variation of strength more then load, and base metal were influenced by load. It is confirmed that the allowable stress range calculating with factor of safety based an reliability is conservative.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.487-493
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• 2017

The main purpose of this study is to evaluate the main parameters involved in the asphalt pavement distresses, including IRI (International Rough Index), fatigue, and permanent deformation. The main parameters are the region (Seoul and Busan), traffic level, asphalt binder, maximum aggregate of surface course, thickness of the surface course and base. A total of 64 case studies were carried out under the auspices of the KPRP (Korea Pavement Research Program). From the analysis of the KPRP test results, the key factors for the asphalt pavement distress were determined. Considering the effect of one variable in the basic condition, asphalt binder was the major factor having an effect on the distresses for an AADT (Annual Average Daily Traffic) of 5000 in the Seoul area. Among the remaining factors, the results were found to be in the order of the base layer thickness (A), surface layer thickness (B), and aggregate particle size thickness (D). The same results were obtained for an AADT of 10000. In the case of Busan with an AADT of 5000, the same result was obtained as for Seoul. Among the remaining factors, the results were in the order of the base layer thickness (A), aggregate particle thickness (D), and surface layer thickness (B). Even though there was a slight difference in the effect of the traffic level and region, asphalt binder was the parameter having the greatest effect on the asphalt pavement distress. In the case where the effect of multiple parameters was analyzed, the combination of the asphalt binder and base thickness showed a relatively strong effect.

• The Journal of Korean Obstetrics and Gynecology
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• v.31 no.1
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• pp.1-19
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• 2018

Objectives: The purpose of this study was to investigate the changes of early puerperium symptoms and Blood Stasis Index in women during the first two weeks after childbirth. Methods: 38 women staying at Korean postpartum management facilities were studied. Questionnaires were filled out on the date of arrival and departure. Changes in overall physical conditions including neuropsychiatric, circulatory, digestive, musculoskeletal, and urogenital and breast symptoms as well as Blood Stasis Pattern were studied. Results: 1. Neuropsychiatric symptoms were shown in order of Depressed Feeling, Insomnia, Dizziness, Headache, and Easy to Anger and Nervous on arrival. All symptoms showed improvement after two weeks, without significance. 2. Circulatory symptoms were shown in order of Excessive Sweating, Edema, Fatigue, Hot Flash, Anemic Feeling, Alternating Chills and Fever, Cold Hypersensitivity, Chills, Oppression in the Chest, and Palpitation on arrival. Hot Flash, Excessive Sweating, and Edema showed significant improvement after two weeks. 3. Digestive symptoms were shown in order of Dyspepsia, Dry Mouth, Constipation, and Loss of Appetite. All symptoms showed improvement after two weeks, without significance. 4. Pain of Muscles & Joints showed improvement after two weeks, without significance. Pain of Teeth & Gingiva showed slight worsening after two weeks, without significance. 5. Urogenital and Breast symptoms were shown in order of Wound Pain, Fever and Distending Pain in the Breast, and Lower Abdominal Pain on arrival. All symptoms showed significant improvement after two weeks. 6. Blood Stasis Index showed significant improvement after two weeks. Conclusion: Most symptoms were improved in women staying at Korean postpartum management facilities for two weeks. Hot Flash, Excessive Sweating, Edema, Wound Pain, Lower Abdominal Pain, Fever and Distending Pain in the Breast and Blood Stasis Index showed significant improvement.