• KIEAE Journal
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• v.9 no.1
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• pp.91-97
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• 2009

In this thesis presents the application to the field of Hwangto-used concrete highlighted as an eco-friendly material and performs an experiment in the aspect of construction and quality on the construction for all parts of buildings, rather than for some parts of buildings as shown from existing application and got the conclusion as followings. 1) It was turned out that Hwangto concrete showed lower hydrated heat and arid contraction comparing to those of cement concrete. And this phenomenon is judged to appear high when applied to mass building and huge span structures. 2) The construction of Hwangto concrete is judged to be possible in applying to constructions since the mechanical construction seems to be possible by using pump car and ready-mixed concrete which are used at the practical sites at the moment. 3) The pockmarks appearing on the exposure surface were about 2% of total area. This has great cohesion by Hwangto concrete but is judged that it will be improved through enough vibration stamping. Through the experiments of quality and construction of Hwangto concrete as environment-friendly construction materials, it is possible to judge modernized application of Hwangto concrete. It is in need of more studies about economical efficiency, structural stability, design application, etc. afterwards.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.3
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• pp.405-417
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• 2015

Objectives: The aim of this study is to evaluate the association between physical factors, working conditions and occupational injuries among Korean workers. Methods: We used data from the 2nd Korean Working Conditions Survey, conducted in 2010. A total of 7,114 workers over 15 years of age were selected from among 10,019 Korean workers. The participants were interviewed using questionnaires. A multiple logistic regression model was used to analyze the associations among physical factors, working conditions and occupational injuries. Results: After the adjustment of socio-demographic factors, the odds ratio of injuries through physical factors such as vibration (adjusted Odds Ratio [aOR] 4.037, 95% CI 2.30-7.09), noise (aOR 4.562, 95% CI 2.64-7.89), high temperature (aOR 3.262, 95% CI 1.86-5.73), and low temperature (aOR 3.358, 95% CI 1.76-6.41) were greater in the exposed group than in the non-exposed group. The odds ratios of occupational injury(aOR 5.272, 95% CI 3.19-8.7 for very high speed work, aOR 3.303, 95% CI 1.95-5.60 for tight deadlines, and aOR 3.641, 95% CI 1.72-7.70 for not enough time to work) increased with increased work demands. Conclusions: In this study, physical factors such as vibration, noise, and high and low temperatures were significantly correlated with occupational injuries according to the increase in exposure intensity(p for trend <0.001). Also, working conditions such as high-speed work, tight deadlines and insufficient time to work showed significant associations with occupational injuries(p for trend<0.001).

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.2
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• pp.178-187
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• 2016

Objectives: Diisocyanates are a potent inducer of diseases of the airways, especially asthma. In this study, toluenediamine(TDA) and methylenedianiline(MDA) in urine were evaluated as biomarkers of exposure to tolunenediisocyanate(TDI) and methylenediphenyl diisocyanate(MDI), respectively. Methods: Workers exposed to TDI and MDI, as well as non-occupationally exposed subjects, were studied and pre- and post-shift urine samples were collected from 8 control subjects and 8 workers from a factory which manufactures polyurethane products for reducing noise and vibration in automobiles. Airborne TDI and MDI(n=8) were sampled on solvent-free glass filters impregnated with n-butylamine and detected by liquid chromatography atmospheric pressure ionization tandem mass spectrometry. Urinary TDA and MDA were detected as pentafluoropropionic acid anhydride(PFPA) derivatives by liquid chromatography electrospray ionization tandem mass spectrometry. Results: The median levels of urinary 2,6-TDA(p<0.001), 2,4-TDA(p=0.001), and MDA(p<0.001) of workers in post-shift samples were significantly higher than those of controls. The median levels of urinary 2,6-0TDA($0.63{\mu}g/g$ creatinine vs $0.34{\mu}g/g$ creatinine, p=0.017) and MDA($4.21{\mu}g/g$ creatinine vs $3.18{\mu}g/g$ creatinine, p=0.017) of workers in post-shift samples were significantly higher than those of the pre-shift samples. There were significant correlations between the urinary 2,6-TDA, 2,4-TDA, and MDA of workers in post-shift samples and the airborne 2,6-TDI(rho=0.952, p<0.001), 2,4-TDI(rho=0.833, p=0.001), and MDI(rho=0.952, p<0.001). Conclusions: These urinary diamines, metabolites of diisocyanates, in post-shift samples were useful biomarkers to assess occupational exposure to diisocyanates.

• The Journal of Korean Physical Therapy
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• v.3 no.1
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• pp.123-149
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• 1991

This study has been attempted to be helpful for the back rehabilization of Korean workers by analyzing the general, occupational, social aspects of low back pain and to identify possible risk factors for back pain in White and Blue collar workers. The primary data were collected from 380 workers in Seoul city by means of a Questionnaire with random which was distributed from March 10 to 31, 1990. For the test of statistical significance, chi-square analysis was used to compare the back pain characteristics between above two groups. The results were as follows : 1. The incidence of low back pain in all walkers studied was $79.7\%$. The incidence of Blue collar with low back pain $(87.2\%)$ was higher than that of White collars $(75.0\%)$. 2. With regard to the relationship of back pain to the occupational characteristics, statistically significant differences were observed between workers with and without back pain concerning the job factors on work-time, job satisfaction, mental stress, chair fittness, work posture, work rotation, weight lifting, monotonous repetitive movements, vibration, and heavy noise (p<0.05). 3. With regard to the relationship of back pain to the social characteristics, there were no differences with respect to having car, personality types, drinking habits, and leisure-time activities. However, significant differences were showed between no pain and pain groups for the using bed, sleeping posture, traffic time amount, walking health state, smoking habits, and physical exercise (p<0.05). 4. The comparative analysis of back pain related to work factors showed highly significant differences with respect to mental stress, chair fittness, work posture, trunk rotation, weight lifting, monotonous repetitive work in White collar group (p<0.01) ; and job satisfaction, mental stress, trunk rotation, weight lifting, monotonus repetitive work, exposure to vibration and heavy noise in Blue collar group(p<0.01). 5. The comparative analysis of social factors in two groups showed differences with respect to the using bed, sleeping posture, walking amount, health state, physical exercise, smoking habits in White cellar group (p<0.05) ; and walking amount, traffic time amount, health state, smoking habits, physical exercise in Blue cellar group (p<0.05). 6. In regard to the general aspects of back pain between two groups, there were differences concerning etiolgy of back pain, counselling partners, treatment types, and sick-leaves(p<0.05), except pain duration, and awareness of back pain.

• Safety and Health at Work
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• v.9 no.1
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• pp.75-78
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• 2018

Background: To identify work sectors with high risk for work-related musculoskeletal disorders (MSDs) in Korean men and women. Methods: We analyzed nationwide data to identify ergonomic risk factors in Korean employees. In particular, we analyzed data on exposure to five ergonomic risk factors (painful/tiring postures, lifting/moving heavy materials, standing/walking, repetitive hand/arm movements, and hand/arm vibration) according to employment sector, sex, and age, using the 2014 Fourth Korean Working Conditions Survey. We also used workers' compensation data on work-related MSDs in 2010, which is available by sex. Results: The different work sectors had different gender distributions. "Manufacturing" (27.7%) and "construction" (11.3%) were dominated by males, whereas "human health and social work activities" (12.4%), "hotel and restaurants" (11.7%), and "education" (10.4%) were dominated by females. However, "wholesale and retail trade" and "public administration and defense" employed large numbers of males and females. Furthermore, the work sectors with a greater proportion of work-related MSDs and with multiple ergonomic risk factors were different for men and women. For men, "construction" and "manufacturing" had the highest risk for work-related MSDs; for women, "hotel and restaurants" had the highest risk for work-related MSDs. Conclusion: Ergonomic interventions for workers should consider gender and should focus on work sectors with high risk for MSDs, with multiple ergonomic risk factors, and with the largest number of workers.

• Coupled systems mechanics
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• v.4 no.2
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• pp.173-189
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• 2015

In reality, masonry infill modifies the seismic response of reinforced concrete (r.c.) frame structures by increasing the overall rigidity of structure which results in: increasing of total seismic load value, decreasing of deformations and period of vibration, therefore masonry infill frame structures have larger capacity of absorbing and dissipating seismic energy. The aim of the paper is to explore and assess actual influence of masonry infill on seismic response of r.c. frame structures, to determine whether it's justified to disregard masonry infill influence and to determine appropriate way to consider infill influence by design. This was done by modeling different structures, bare frame structures as well as masonry infill frame structures, while varying masonry infill to r.c. frame stiffness ratio and seismic intensity. Further resistance envelope for those models were created and compared. Different structures analysis have shown that the seismic action on infilled r.c. frame structure is almost always twice as much as seismic action on the same structure with bare r.c. frames, regardless of the seismic intensity. Comparing different models resistance envelopes has shown that, in case of lower stiffness r.c. frame structure, masonry infill (both lower and higher stiffness) increased its lateral load capacity, in average, two times, but in case of higher stiffness r.c. frame structures, influence of masonry infill on lateral load capacity is insignificant. After all, it is to conclude that the optimal structure type depends on its exposure to seismic action and its masonry infill to r.c. frame stiffness ratio.

• Journal of the Society of Disaster Information
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• v.18 no.3
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• pp.478-486
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• 2022

Purpose: Although the working environment is measured at the construction site, only a few noise and vibration that are typically exposed for each process are performed without measuring the working environment by segmenting the exposed harmful factors. Therefore, it is intended to find the harmfulness of silicon oxide dust, which is most exposed at construction sites, and the complementary points of improvement measures currently being implemented at construction sites. Method: The status was analyzed using the actual condition survey report issued by the Korea Occupational Health Corporation and the Korea Occupational Health Association and data from the work environment measurement institution, and compared and analyzed with the rules on work environment measurement of the Occupational Safety and Health Act. Result: The harmfulness of silicon oxide dust was identified and improvement measures were derived. Conclusion: It is expected that occupational diseases against silicon dust can be reduced if the harmfulness of silicon oxide dust at construction sites is derived and improvement measures are actively applied at the site.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.1
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• pp.9-17
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• 2022

As the COVID-19 pandemic situation worsens, the time spent indoors increases, and the exposure to indoor environmental pollution such as indoor air pollution and noise also increases, causing problems such as deterioration of human health, stress, and discord between neighbors. This paper designs and implements a system that measures and monitors indoor air quality and noise, which are representative evaluation criteria of the indoor environment. The system proposed in this paper consists of a particulate matter measurement subsystem that measures and corrects the concentration of particulate matters to monitor indoor air quality, and a noise measurement subsystem that detects changes in sound and converts it to a sound pressure level. The concentration of indoor particulate matters is measured using a laser-based light scattering method, and an error caused by temperature and humidity is compensated in this paper. For indoor noise measurement, the voltage measured through a microphone is basically measured, Fourier transform is performed to classify it by frequency, and then A-weighting is performed to correct loudness equality. Then, the RMS value is obtained, high-frequency noise is removed by performing time-weighting, and then SPL is obtained. Finally, the equivalent noise level for 1 minute and 5 minutes are calculated to show the indoor noise level. In order to classify noise into direct impact sound and air transmission noise, a piezo vibration sensors is mounted to determine the presence or absence of direct impact transmitted through the wall. For performance evaluation, the error of particulate matter measurement is analyzed through TSI's AM510 instrument. and compare the noise error with CEM's noise measurement system.

• Journal of Animal Reproduction and Biotechnology
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• v.38 no.2
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• pp.84-88
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• 2023

Because multiple ovulation embryo transfer (MOET) in cattle includes several benefits such as wide spreading of genetically superior offspring for long distance, this biotechnological method has been widely applied to Hanwoo. When the recipients are not stayed close after embryo recovery from donor, the embryos are moved to other farms via several vehicles (car, train, and airplane). However, air travel induces lesser oxygen level, increased vibration, lower air pressure, higher noise, and increased exposure of cosmic radiation to living things than ground level. It was still unknown that fresh embryos obtained from multiple ovulation of Hanwoo could maintain their fertility after being transported via air plane, the present case report introduced a clinical case of MOET in Hanwoo after shipping fresh embryos via air transportation. The donor was multi-ovulated via follicle-stimulating hormone series of injection, which was followed by a gonadotrophin-releasing hormone injection and artificial insemination twice. The embryos were recovered by the uterine flushing, packed in ministraws, transported to recipients for 6 h including 1 h air flight, and then transferred to the synchronized recipients. During pregnancy diagnosis of early gestation period, 5 of 7 recipients (71.4%) presented no heat signs and showed fetal sacs with fluid under transrectal ultrasonography. After normal gestation period, all recipients naturally delivered healthy calves (male n = 2 and female n = 3) without abortion, stillbirth, and premature birth. The present case report indicated that transportation of fresh embryos for MOET via domestic flight in Korea did not affect to their fertility.

• Tribology and Lubricants
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• v.40 no.4
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• pp.111-117
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• 2024

Due to global CO₂ emission reductions and fuel efficiency regulations, the trend toward transitioning from internal combustion engine vehicles to electric vehicles (EVs) has accelerated. Consequently, the problem of EV failures has become a focal point of active research. The parasitic capacitance generated during motor-shaft rotation induces voltage that deteriorates the raceway and ball surfaces of bearings, causing electrical damage in EVs. Despite numerous attempts to address this issue, most studies have been conducted under high viscosity lubricant and low load conditions. However, due to factors such as high-speed operation, rapid acceleration and deceleration, motor heating, and motor system-decelerator integration, current EV applications have shown diminished stability in lubrication films of motor bearings, thereby leveraging the investigation to address the risk of electrical damage. This study investigates the electrical damage to rolling bearing elements in EV motor drive systems. The experimental analysis focuses on the effects of electric currents and operational loads on bearing integrity. A test rig is designed to generate high-rate voltage specific to a motor system's parasitic capacitance, and bearing samples are exposed to these currents for specified durations. Component evaluation involves visual inspections and vibration measurements. In addition, a predictive model for electrical failure is developed based on accumulated data, which demonstrates the ability to predict the likelihood of electrical failure relative to the duration and intensity of current exposure. This in turn reduces uncertainties in practical applications regarding electrical erosion modes.