• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.611-620
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• 2006

The composite two plate-girder bridges are generally defined as a non-redundant load path structure because the bridge can collapse if one of the two girders is seriously damaged by a fatigue crack. In this paper, a numerical study on the evaluation of the after-fracture redundancy of the composite two-girder bridges was accomplished. The evaluation has been performed on the simple and three-span continuous bridges with I-section cross beams which serve as transverse bracing, and with or without the bottom lateral bracing system. The load carrying capacities of the intact and damaged bridges with or without lateral bracing were evaluated from material and geometric nonlinear analysis, respectively and the redundancy was evaluated for each case. It was acknowledged from the analytical results that both simple and continuous intact two-girder bridges have sufficient redundancy even without lateral bracing, but it takes an important role to improve the redundancy of damaged bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.445-451
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• 2006

This study was conducted to develop the interlayer mixture that absorbs the stress between the old concrete pavement and the asphalt overlay pavement layer. The elasticity, the flexibility, the consistency and the impermeability is required for high-elastic Stress Absorbing Interlayer(HSAI) to absorb and disperse the stress that causes the flexural and horizontal movements of the joint and the crack. The HSAI developed from foreign product was satisfied with the design criteria. The specimens using the HSAI showed the significant reduction of the reflective crack compared those not using the HSAI. The significance included that the life of shear failure and horizontal displacement resistance increased 4 times. The life of the share failure increased to 5 times and the horizontal displacement increased to 9 times according to the selection of surface course material which showed the excellence of the HSAI.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.4
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• pp.502-516
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• 2023

Objectives: The purpose of this study was to investigate occupational exposure to chemical and health status of foreign workers in Korea. Methods: The data were collected from survey of general characteristics, job-related characteristics, work environment-related characteristics of 180 foreign workers who have been working at manufacturing industries in Korea in 2022. The data were analyzed using Rex. Results: Among the 180 participants, men accounted for more than women by 71.7% (129 people). Most of them are Vietnamese or Filipino and most of them graduated from high school. 116 of all participants are exposed to chemicals at work. The most prevalence rate of subject's health problems were backache (61.0%), headache (53.9%), fatigue (68.0%). Controlling for age, the number of physical health problems experienced in the last year was associated with BMI (r=0.184, p=0.049), and the number of mental health problems experienced in the past year (r=0.056, p<0.001) and all showed significant positive (+) correlations. The number of chemical products handled under age control showed a significant negative (-) correlation with working hours (r=0.207, p=0.027) and BMI (r=0.214, p=0.022) and showed a significant positive (+) correlation. Conclusions: The results of this study provided the latest update on the health status of foreign workers in Korea. It is also the first survey to attempt to assess the exposure of foreign workers to chemicals.

• Journal of Preventive Medicine and Public Health
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• v.42 no.2
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• pp.89-95
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• 2009

Objectives : To assess the protective effects of wearing protective devices among the residents and volunteers who participated in the cleanup of the Hebei Spirit oil spill. Methods : A total of 288 residents and 724 volunteers were surveyed about symptoms, whether they were wearing protective devices and potential confounding variables. The questionnaires were administered from the second to the sixth week following the accident. Spot urine samples were collected and analyzed for metabolites of 4 volatile organic compounds(VOCs), 2 polycyclic aromatic hydrocarbons(PAHs), and 6 heavy metals. The association between the wearing of protective devices and various symptoms was assessed using a multiple logistic regression adjusted for confounding variables. A multiple generalized linear regression model adjusted for the covariates was used to test for a difference in least-square mean concentration of urinary biomarkers between residents who wore protective devices and those who did not. Results : Thirty nine to 98% of the residents and 62-98% of volunteers wore protective devices. Levels of fatigue and fever were higher among residents not wearing masks than among those who did wear masks(odds ratio 4.5; 95% confidence interval 1.23-19.86). Urinary mercury levels were found to be significantly higher among residents not wearing work clothes or boots(p<0.05). Conclusions : Because the survey was not performed during the initial high-exposure period, no significant difference was found in metabolite levels between people who wore protective devices and those who did not, except for mercury, whose biological half-life is more than 6 weeks.

• Journal of Life Science
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• v.27 no.2
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• pp.247-266
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• 2017

Cordyceps is a traditional Chinese medicinal herb well-known in China, Korea and Japan since B.C. 2,000. The original entomopathogenic fungus, Cordyceps sinensis belonging to the genus Cordyceps could not be found inside Korean peninsula due to the absence of the host insect for the corresponding entomogenous fungus. The development of artificial production methods of Korean type Cordyceps using the silkworm Bombyx mori as in vivo culture medium for the the entomopathogenic fungus Paecilomyces tenuipes is the first, and wonderful occasion in the research history of insect industry of this global world. The aim of this article is to review the historical research background, mass-production methods, and pharmacological effects of the silkworm-dongchunghacho (Paecilomyces tenuipes) which is a newly developed Korean medicinal insect-borne mushroom, and another non-insect-borne medicinal mushroom (Cordyceps militaris and Cordyceps pruinosa). Their biological actions include anti-tumor, immunostimulating, anti-fatigue, anti-stress, anti-oxidant, anti-aging, anti-diabetic, anti-inflammatory, anti-thrombosis, hypolipidaemic and insecticidal effects. The bioactive principles are protein-bound polysaccharides (hexose, hexosamin), cordycepin, D-manitol, acidic polysaccharide etc. Protein-bound polysaccharides and n-butanol fractions were demonstrated to show a significant anti-tumor activities but did not show a cytotoxicities. D-mannitol exhibited a significant prolongation of the life span in tumor bearing mice. Ergosterol did not show an efficient anti-tumor activity, but showed a significant phagocytosis enhancing activity. Anti-tumor activity of silkworm-dongchunghacho might be attributed to immuno-stimulating activities rather than cytotoxic effects [164]. Also this review comprises the breeding of Dongchunghacho varieties, optimization of culture conditions, improvement of learning and memory by Dongchunghacho, application of them as foods and chemical constituents.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.63-72
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• 2013

HTB (hybrid truss bridge) steel truss webs instead of concrete webs in prestressed box girder bridges has been widely used in, because of its structural benefit such as relatively less self-weight and good aesthetics due to open web structure. Since the core technology of this bridge is the connection system between concrete slabs and steel truss members, several connection systems were proposed and experimentally evaluated. Also, the selected joint system was applied to the real bride design and construction. The researches were performed on the connection system, since it can affect the global behavior of this bridge such as flexural and fatigue behaviors as well as the local behavior around the connection region. The evaluation study showned that HTB applied to a curved bridge or a eccentric loading bridge, characteristic has a weak torsional capacity compared to an ordinary PSC box girder bridges due to the open structure of HTB. In this study, three box shaped hybrid truss specimens were made and the torsional test and evaluation for them were performed in order to find out the torsional behavior of HTB according to the connection system.

• Korean Journal of Community Nutrition
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• v.23 no.4
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• pp.289-301
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• 2018

Objectives: The aim of this study was to examine the current status of consumption of energy drinks among college students and investigate the effects of general environmental factors, health behavior factors, caffeine knowledge levels, and perceived stress levels on consumption of energy drinks. Methods: A survey was conducted among a total of 479 college students in Gwangju, using self-administered questionnaires. The questionnaire consisted of items about general environmental factors, health behavior, caffeine knowledge, perceived stress, and energy drink consumption behaviors. Results: 69.1% of participants experienced consumption of energy drinks, and specifically 82.8% of male students and 54.1% of female students experienced consumption of energy drinks (p<0.001). The reasons for drinking energy drinks were found to be recovery from fatigue, curiosity, taste, habit, thirst relief, and stress relief. In addition, 40.7% of participants experienced drinking energy drinks mixed with alcohol, and specifically 48.6% of male students and 27.4% of female students reported drinking energy drinks with alcohol (p<0.001). Moreover, 51.5% of participants responded that they experienced the effects of energy drinks, 31.9% reported experiencing adverse effects, and 41.1% were found to perceive the health risks. As a result of the assessment of caffeine knowledge, the participants showed a high level of knowledge of the arousal effect (77.7%) and the concentration increasing effect (70.8%) of caffeine, whereas they exhibited a low level of understanding of the health problems due to caffeine (32.6%) and adequate caffeine intake levels (24.4%). The higher levels of consumption experience of energy drinks was associated with higher body mass indexes (BMI) (p<0.01), higher academic years (p<0.01), lower levels of interest in health (p<0.05), smoking (p<0.001), alcohol consumption (p<0.05), and higher levels of perceived stress (p<0.05). Conclusions: The risk groups related to consumption of energy drinks among college students were identified as male students rather than female students, students in the third or fourth year of study associated with increased stress levels, and students with negative health behaviors. Therefore, support for diverse health and nutrition education for college students is required along with the improvement of internal and external environments of schools in order for college students to manage increased stress levels due to the schoolwork and preparation for employment and maintain positive health behaviors.

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.340-347
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• 2013

This paper studied the causes of job stress of driving crews working in Metropolitan Transit Authorities in Daejeon, Daegu, Seoul Metro Line 9, and Incheon, analyzing psychological, physical, and environmental factors, along withdriving crews' assignments. Regarding driving crews' assignments, it was found that driving crews had strong senses of obligation for their job, and hence their aptitude for their job was in accordance, and also it was found that most driving crews worked devotedly with a desirable occupational view and pride. However, psychological and physical factors that contributed to stress were identified: lack of sleep, high task burden, physical fatigue, and boring daily life. Furthermore, the driving crews' irregular working conditions and irregular meal time and burden related to on-time transit service with prolonged immobilization raised their stress levels. In terms of external environmental factors, it was found that driving crews' anxiety due to possible accidents caused a roughly four-fold increase in stress levels compared to other factors. Furthermore, personnel system and salary issue were also found to be closely related to the driving crews' job stress.

• Journal of Korean Society of Disaster and Security
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• v.14 no.4
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• pp.47-60
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• 2021

Recently, as the occurrence frequency of sudden floods due to climate variability increased, the damage of aging chuteway slabs of spillway are on the rise. Accordingly, a wide array of field survey, hydraulic experiment and numerical simulation have been conducted to find the cause of damage on chuteway slabs. However, these studies generally reviewed the flow characteristics and distribution of pressure on chuteway slabs. Therefore the derivation of damage on chuteway slabs was relatively insufficient in the literature. In this study, the cavitation erosion and hydraulic jacking were assumed to be the causes of damage on chuteway slabs, and the phenomena were reproduced using 3D numerical models, FLOW-3D and COMSOL Multiphysics. In addition, the cavitation index was calculated and the von Mises stress by uplift pressure distribution was compared with tensile and bending strength of concrete to evaluate the possibility of cavitation erosion and hydraulic jacking. As a result of numerical simulation on cavitation erosion and hydraulic jacking under various flow conditions with complete opening gate, the cavitation index in the downstream of spillway was less than 0.3, and the von Mises stress on concrete was 4.6 to 5.0 MPa. When von Mises stress was compared with tensile and bending strength of concrete, the fatigue failure caused by continuous pressure fluctuation occurred on chuteway slabs. Therefore, the cavitation erosion and hydraulic jacking caused by high speed flow were one of the main causes of damage to the chuteway slabs in spillway. However, this study has limitations in that the various shape conditions of damage(cavity and crack) and flow conditions were not considered and Fluid-Structure Interaction (FSI) was not simulated. If these limitations are supplemented and reviewed, it is expected to derive more efficient utilization of the maintenance plan on spillway in the future.

• Journal of Korean Academy of Nursing
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• v.20 no.2
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• pp.131-141
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• 1990

Recently, the rate of cesarean section in Korea has been increasing. The results of several previous studies in foreign countries on the emotional responses of cesarean section mothers showed that they might experience difficulties in the mother- infant interaction due to fatigue, lack of early mother - infant interaction, disappointments, anger, feelings of loss of control, and other factors. Human behavior is said to be determined by one's self concept, and self concept is influenced by both internal and external environmental factors. A scale to measure the self concept of cesarean section mothers was needed in order to identify those who might have difficulties in the mother- infant interactions in future. The purposes of this study were to develop a measuring scale, and to test its reliability and validity. The process of this study was as follows. A structured interview was done with 50 cesarean section and vaginal delivery mothers to find their state of emotional reaction after giving birth to their babies. Based on the results of the interviews, a 50 items Likert scale was developed. The self concept of 268 cesarean section and vaginal delivery mothers who were hospitalized at six hospital in seoul were measured, during the period between Feb. 1 and April 30. Reviewing the discriminating power of each item by means of crosstabulation, ten items were selected for the final scale. The reliability and validity of this ten item scale were tested by Cronbach's alpha and t-test, using spss pc＋package. The results of this study and recommendation are as follows. 1. The ten selected items were as follows. I feel pains in my breast. (－) I have a good appetite now. (＋) I feel pains in my flank. (－) I feel fine now. (＋) My body seems to have returned to its prepregnant state. (＋) Thinking of the delivery process, I feel sorry. (－) I want to hold my baby in my arms. (＋) I want to keep my own life, even if I became a mother. (－) I want to delegate the care of the baby to my mother / mother in law. (－) I think baby is my alter ego. (＋) 2. The reliability of this scale was tested by Cronbach's alpha, and the coefficient of this scale was .8066. 3. The construct validity of this scale was tested by means of known group methods. The value of self concept for cesarean section mother was significantly lower than for vaginal delivery mothers(t＝-5.51, df＝266, p＝0.007). 4. The criterion validity of this scale was tested indirectly. Though this scale could discriminate the differences in the self concept between cesarean section and vaginal delivery mothers, the five items on the personal self concept scale didn's show any differences between cesarean section and vaginal delivery mothers. Therefore, the study indicates that those who shows lower values in the personal self concept measurement, that is, lower than 12.03 points, could be regaled as “risk mothers” 5. Further studies using this scale to clarify the influencing factors on negative self concept are strongly recommended.