• Explosives and Blasting
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• v.31 no.2
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• pp.32-39
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• 2013

Generally, The way of long hole blasting is carried out in coal-face, basic excavation for dam, mine etc. Recently, this long hole blasting has been implemented in civil engineering for efficiency & economic feasibility. National express no.600 of Pusan outer high-express ${\bigcirc}$ construction site with four lanes of the length of 8km was also a site applied by long hole blasting. But After blasting, tunnel advance rate is less than 75%. As a result of that, Follow-up working time is influenced. Thereby, The total of working process is significantly so increased that planned excavation cannot be implemented many times. For not only improve excavation rate but reduce working process time in job site, we introduce blasting case which apply the ${\phi}36mm$ explosive suited for high desity of charging among long hole blasting in order to overcome mentioned problem.

• Wind and Structures
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• v.19 no.1
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• pp.1-14
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• 2014

Rail-mounted cranes can be easily damaged by a sudden gust of wind while working at a running speed, due to the large mass and high barycenter positions. In current designs, working rail-mounted cranes mainly depend on wheel braking torques to resist large wind load. Regular brakes, however, cannot satisfactorily stop the crane, which induces safety issues of cranes and hence leads to frequent crane accidents, especially in sudden gusts of wind. Therefore, it is necessary and important to study the braking performance of working rail mounted cranes under wind load. In this study, a simplified mechanical model was built to simulate the working rail mounted gantry crane, and dynamic analysis of the model was carried out to deduce braking performance equations that reflect the qualitative relations among braking time, braking distance, wind load, and braking torque. It was shown that, under constant braking torque, there existed inflection points on the curves of braking time and distance versus windforce. Both the braking time and the distance increased sharply when wind load exceeded the inflection point value, referred to as the threshold windforce. The braking performance of a 300 ton shipbuilding gantry crane was modeled and analyzed using multibody dynamics software ADAMS. The simulation results were fitted by quadratic curves to show the changes of braking time and distance versus windforce under various mount of braking torques. The threshold windforce could be obtained theoretically by taking derivative of fitted curves. Based on the fitted functional relationship between threshold windforce and braking torque, theoretical basis are provided to ensure a safe and rational design for crane wind-resistant braking systems.

• Journal of the Korean Data and Information Science Society
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• v.26 no.6
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• pp.1271-1281
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• 2015

Competing risk analysis is widely applied to analyze a failure time with more than two causes. This paper discusses the application of a competing risk model to a economic activity state of workers with occupational injuries. In particular, main interest is to estimate the distribution of restarting time two kinds of economic activities, (i) returning to original working place and (ii) finding a new job. In this paper, we applied a cumulative incidence function to evaluate their patterns under several individual factors and working place's factor. Furthermore, a subdistributional regression model is applied to estimate the effect of these factors on the returning time. According to result, worker with higher education, younger age and longer working period had a higher chance to return an original working place while one with more severe injuries and skilled laborer had longer returning time to an original working place.

• Korean Journal of Child Studies
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• v.7 no.1
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• pp.1-23
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• 1986

The present study investigated the current child care practices of professional working mothers in Korea and their needs for substitute child care outside the home. Three hundred twenty-two professional working mothers who have children under 6 years of age in Seoul, Pusan, Taegu, and Taejon were surveyed with the use of a questionnaire. It was found that during their working hours, most of the professional working mothers put their children in the care of either the paternal or the maternal grandmothers. Others put the children in the care of a full-time housekeeper or a part-time housekeeper. While all the mothers had worked out a way to care for their children, almost all of them would use day care if facilities were available. Specifically, 42 per cent prefer child care at their work site, 21 per cent prefer family day care, and only 3 per cent indicated that they would not use any child care facilities. Most of the working mothers think that their employer should manage the day care program. Others prefer social agency or government management. Regarding costs, most prefer that costs should be split 50-50 between the employer and the family. In addition, professional working mothers wanted quality programs with educational components rather than mere custodial care. It was concluded that variety in types of quality child care programs should be available to provide working mothers the options of choosing what they want for their children. The main type of programs suggested by this study is work site based child care for children under 3 years of age. The existing law for the Saemaul Nursery School program should be implemented so as to include programs for children under 3.

• Journal of the Ergonomics Society of Korea
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• v.30 no.5
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• pp.671-681
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• 2011

Objective: The purpose of this study is to compare the workload level at each lower limbs posture and suggest the ergonomic workstation guideline for working period by evaluating the imbalanced lower limbs postures from the physiological and psychophysical points of view. Background: Many workers like welders are working in various imbalanced lower limbs postures either due to the narrow working conditions or other environmental conditions. Method: Ten male subjects participated in this experiment. Subjects were asked to maintain 3 different lower limbs postures(standing, squatting and bending) with 3 different working conditions(balanced floor with no scaffold, imbalanced floor with 10cm height of scaffold, and imbalanced floor with 20cm height of scaffold). EMG data for the 4 muscle groups(Retus Femoris, Vastus Lateralis, Tibialis Anterior, Gastrocnemius) from each lower limbs posture were collected for 20 seconds every 2 minutes during the 8 minutes sustaining task. Subjects were also asked to report their discomfort ratings of body parts such as waist, upper legs, lower legs, and ankle. Results: The ANOVA results showed that the EMG root mean square(RMS) values and the discomfort ratings(CR-10 Rating Scale) were significantly affected by lower limbs postures and working time(p<0.05). The correlation was analyzed between the EMG data and the discomfort ratings. Also, prediction models for the discomfort rating for each posture were developed using physical condition, working time, and scaffold height. Conclusion: We strongly recommend that one should not work more than 6 minutes in a standing or squatting postures and should not work more than 4 minutes in a bending posture. Application: The results of this study could be used to design and assess working environments and methods. Furthermore, these results could be used to suggest ergonomic guidelines for the lower limbs postures such as squatting and bending in the working fields in order to prevent fatigue and pain in the lower limbs body.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.32 no.4
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• pp.325-339
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• 2022

Objective: This study was to perform to identify the distribution characteristics and related factors of work-related low back pain among manufacturing workers in Korea. Methods: We analyzed the third(2011) through sixth(2020) Korean Working Conditions Survey. This study examined changes in the prevalence of work-related low back pain among manufacturing workers and related factors, including demographic characteristics and working conditions. Results: The prevalence of work-related low back pain showed a general tendency to increase during the study periods except for the 5th wave. The prevalence of work-related low back pain was higher in women than in men. The prevalence increased with increasing age and decreased with higher educational attainment. This trend was observed in all survey waves. The prevalence ratios for work-related low back pain according to working conditions varied over the survey period. In general, workers with manual jobs, long working hours, and exposure to tired or painful postures showed relatively higher prevalence ratios than did their counterparts. Providing Information on health and safety, perception that work affects health, and experience of presenteeism were identified as influencing factors for work-related low back pain. Although the working environment is improving, work-related back pain is on the rise. A multifaceted study on risk factors for work-related low back pain is needed. Conclusion: Work-related low back pain is a significant factor affecting the working population's quality of life. The prevalence of work-related low back pain showed a tendency to increase during the study periods. A multifaceted study on risk factors for work-related low back pain is needed.

• Korean Journal of Culture and Social Issue
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• v.28 no.3
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• pp.441-481
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• 2022

This study attempted to explore the experience related to the work-family balance of working moms during the COVID-19 period. To this end, in-depth interviews were conducted by recruiting 17 part-time and full-time working moms with at least 1 child under the age of 13. As a result of analyzing the data using the method of grounded theory, 106 concepts, 50 subcategories, and 24 categories were derived. The central phenomenon that working moms experienced in the process of work and family balance were "physical and emotional exhaustion", "anxiety and guilt about not doing well in situations of role conflicts between various roles", "job crisis experienced by working mothers" and "deepening family conflicts". The process of working moms overcoming the central phenomenon and achieving work-family balance was identified as five stages: the 'shock and confusion stage', the 'struggling stage', the 'actively coping and making compromise stages', the 'acceptance stage', and the 'post-traumatic growth stage'. Based on these results, discussions on the work-family balance of working mothers during the COVID-19 period was dealt as well as suggestions for follow-up studies.

• Journal of Korean Society of Disaster and Security
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• v.14 no.4
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• pp.1-7
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• 2021

Although the working environment has changed significantly compared to the past, such as the implementation of the five-day work week and the aging of the population, it is not reflected in the current industrial accident index calculation such as frequency rate, severity rate, and safe T-score. In this study, statistical data were used to understand time-series trends such as increase in life expectancy, working age, shortening of working hours, and average age of death by accident. As a result of time series trend analysis of statistical data, life expectancy increased to 83.3 years, and the legal working age was raised to 65 years due to the aging of the population. Also, with the advent of the 5-day work week since 2001, the average annual working hours decreased to 2008.1 hours. It can be confirmed through statistical data that these phenomena are applied to the current working environment due to a complex action, and these environmental changes affect the calculation results of the industrial accident index.

• Journal of Yeungnam Medical Science
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• v.4 no.2
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• pp.139-148
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• 1987

The community health practitioners (CHP) play an important role in primary health care services to the underserved population in rural area. Time and motion study of 26 CHPs in Kyungpook Province was conducted through work diary method for 6 consecutive days from the time they arrived until they left the primary health post(PHP) during the past 3 weeks from November 16 to December 5, 1987. The allocation of activity time by working category, service category, location of activity and CHP's function was analyzed according to the characteristics of CHPs i. e., age, marital status and experience as CHP. The major findings are as follows : The mean activity time per CHP in a week was 2,918 minutes. The length of their working hours was longer for older, married and more experienced CHPs than others. About 80% of the CHP's activities took place within the PHP and only about 20% occured outside of the PHP. Working hours for the outdoor activities were longer for younger, single and less experienced CHPs than others. The allocation of activity time by working category showed 46.3% in the technical work and 18.7% in the administrative work. Working hours for the technical activities were longer for younger, single and less experienced CHPs than others. The percentage of activity time revealed greatest as much as 63.1% for direct patient care in technical work and 61.6% for record keeping in administrative work. Of the total working hours in a week, direct patient care and public health activities accounted for 29.2% and 16.2%, respectively. Of the indoor activities, working hours for direct patient care were longer than those for public health activities. However, of the outdoor activities, working hours for public health activities were longer than those for direct patient care. The allocation of activity time by CHP's function showed 49.7% in management of common disease, 31.8% in management of PHP and technical supervision of village health workers, 9.5% in MCH and family planning, 6.6% in community health management and 2.4% in community approach. Based on these findings, it was found that CHPs were mainly working in the PHP with a majority of their time being spent for direct patient care rather than preventive and promotive health cares. To enhance the preventive and promotive health services of the CHPs and to involve the activities for community development, refresher course for CHPs should be reinforced and supervision mechanism of the CHPs should be established and operated in Gun- and province-level.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.4
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• pp.325-329
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• 2015

Purpose: The aim of this study was to compare the film thicknesses of several resin cements as a function of time after mixing and to examine the effect of working time on the film thicknesses. Materials and methods: The film thickness (${\mu}m$) of 4 resin cements (n=10), 1 composite resin (Panavia F 2.0), 3 self-adhesive resin (Clearfil SA luting, Zirconite, RelyX U200) cements was measured at 20-second intervals after mixing of the cements up to 200 seconds under a load of 50 N. Linear regression was fitted to verify the effect of working time on the film thickness of each cement. Data were compared to the working time recommended by manufacturers using Wilcoxon test ($\alpha$=.05). Results: All of the materials showed a positive linear correlation between the film thickness and working time. There was no statistically significant difference between the working time based on our results and the values recommended by the manufacturers even though there was a discrepancy between those two values. Conclusion: The film thickness of resin cements could increase with the increase of working time. Working time to meet the ISO standard of $50-{\mu}m$ maximum film thickness could be different from the manufacturer's recommended value.