• 농업과학연구
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• 제40권3호
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• pp.209-214
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• 2013

This study examined the work time, work posture, and work intensity for the actual measurement step in forest road the design work that was being carried out. The measurement of the forest road was being carried by a team of three workers and a team of four workers. The examination of work time found that the measurement of 1km took about 8 hours for the four-worker team and 12 hours for the three-worker team. The examination of work intensity found that the energy metabolic rates of the three-worker team were lower than four-worker team. Because their energy consumption per minute decreased as their work time and rest time increased. Furthermore, when appropriate rest time was applied according to work time, the energy metabolic rate decreased and the work intensity became lower. The four-worker team was more advantageous from the time and cost aspects of the forest road measurement work. Furthermore, as the rest time was very low compared to the work time, more efficient forest road measurement work would be possible if the work intensity was lowered by considering the rest time when calculating the standard work time.

• Journal of Welding and Joining
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• 제15권1호
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• pp.125-134
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• 1997

This study was conducted by L9 orthogonal array to obtain optimum spray parameters for This study was conducted by L9 orthogonal array to obtain optimum spray parameters for $Cr_3C_2 - 7wt%$(80wt%Ni-20wt%Cr) coating powder. The factors were hydrogen flow rate, oxygen flow rate, gun-to-work distance, powder feed rate. And evaluation methods for the coating were surface roughness, oxygen concentration, micro-hardness, pore size and distribution, low angle ($30^{\circ}$) erosion rate, and microstructure of coating. The optimum HVOF spray conditions were proved as follows : hydroen flow rate ; 681 SLPM, oxygen flow rate ; 215 SLPM $H^2/O^2 ratio= 3.16), gun-to-work distance ; 22cm, powder feed rate; 25g/min. The hardness (Hv300) was 1147 and the erosion rate ($30^{\circ}$degree) was $3.16\times10^{-4}$g/g. It is believed that the optimized spray conditions can be improved the wear-resistance and anti-erosion characteristics of the coating.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1060-1068
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• 2019

This work aims to establish a model of a primary water stress corrosion crack growth rate of Alloy 690 material for the head penetration nozzles of Korean pressurized water reactors. The test material had an inhomogeneous microstructure with bands of fine-grains and intragranular carbides in the matrix of coarse-grains, which was similar to the archive materials of the head penetration nozzles. The crack growth rate was measured from the strain-hardened materials as a function of the stress intensity factor in simulated primary water at various temperatures and dissolved hydrogen contents. The effects of strain-hardening, temperature, and dissolved hydrogen on the crack growth rate were analyzed independently, and were then introduced as normalizing factors in the crack growth rate model. The crack growth rate model proposed in this work provides a key element of the tools needed to assess the progress of a stress corrosion crack when detected in thick-wall Alloy 690 components in Korean reactors.

• 대한안전경영과학회지
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• 제17권3호
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• pp.133-141
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• 2015

This study tried to identify the problems associated with the posture to be analyzed and tried to suggest guidelines for MSDs(Musculoskeletal Disorders) evaluation based on working posture. A total of 50 jobs from 3 different types of industries(electronics, hospitals, automobiles) were used for MSDs evaluation study which was done by 6 observers. Two indexes were applied to identify the problem in this study which were percentage of agreement and counter-time-error rate. Specifically, 'counter-time-error rate' represented a degree of consistency in terms of selecting the posture to be analyzed time after time. Main results of the study were as follows; 1) The average percentage of agreement for representative posture for whole body was relatively higher than that for representative postures for individual body parts, 2) The counter-time-error rate(%) has been reduced as the evaluation process has repeated for the same job. 3) The counter-time-error rate(%) for electronics, hospitals, and automobiles were 63.4%, 61.2%, and 67.3% respectively. 4) The counter-time-error rate(%) for the job with the work cycle of 0.5 to 2 minutes were lower than that of the jobs with the work cycles less than 0.5 minute or greater than 2 minute. 5) The work cycles and the number of trials had significant effects on counter-time-error rate while the types of industries did not have significant effects on counter-time-error rate. Some guidelines could be prepared from the results of the study. Probably, there should have an extension in terms of form and matter for this study in order to have more practical output.

• 한국안전학회지
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• 제15권3호
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• pp.108-114
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• 2000

The work posture impose additional stress upon human workers so that it should be carefully considered in designing works. However, we have a lot of manufacturing plants which convert their standing workplace to sedentary one. To confirm the validity of that trend, the authors conducted an experimental study, and compared the results. The results of the EMG and the self-cognitive symptoms, in general, showed a correspondent trend that the sedentary work posture was rated more comfortable. At the beginning of the work, complaint of the lowerback was higher whereas that of the lower leg and the feet went higher as the time elapsed. If the weight of workpiece were heavier than 500g, increasing rate of bodily discomfort in the sedentary posture were greater than that of the standing posture. In the meanwhile, the standing posture was consistently superior to the sedentary posture in its performance. Thus, in conclusion, for a light assembly work, sedentary work posture would be recommendable because bodily discomfort would be larger irrespective of the small increase of performance increase.

• Annals of Occupational and Environmental Medicine
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• 제35권
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• pp.22.1-22.9
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• 2023

Background: Shift work increases the risk of chronic diseases, including metabolic diseases. However, studies on the relationship between shift work and renal function are limited. The aim of this study was to investigate the association between shift work and a decreased glomerular filtration rate (GFR). Methods: Data were evaluated for 1,324,930 workers who visited the Korean Medical Institute from January 1, 2016 to December 31, 2020 and underwent a health checkup. Daytime workers were randomly extracted at a ratio of 1:4 after matching for age and sex. In total, 18,190 workers aged over 40 years were included in the analyses; these included 3,638 shift workers and 14,552 daytime workers. Participants were categorized into the shift work group when they underwent a specific health checkup for night shift work or indicated that they were shift workers in the questionnaire. The odds ratio was calculated using a conditional logistic regression to investigate the relevance of shift work for changes in GFR. Results: 35 workers in the shift group and 54 in the daytime group exhibited an estimated GFR (eGFR) value of < 60 mL/min/1.73m² (p < 0.01). The difference in eGFR values between two checkups differed significantly depending on the type of work (p < 0.01); the difference in the shift work group (-9.64 mL/min/1.73 m²) was larger than that in the daytime work group (-7.45 mL/min/1.73 m²). The odds ratio for eGFR reduction to < 60 mL/min/1.73 m² in the shift group versus the daytime group was 4.07 (95% confidence interval: 2.54-6.52), which was statistically significant. Conclusions: The results of this study suggest that eGFR decreases by a significantly larger value in shift workers than in daytime workers; thus, shift work could be a contributing factor for chronic kidney disease (CKD). Further prospective studies are necessary to validate this finding and identify measures to prevent CKD in shift workers.

• 대한안전경영과학회지
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• 제20권1호
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• pp.11-21
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• 2018

Safety accidents, which are called industrial accidents in construction work, are often caused by unstable physical and personal conditions combined during preparation and execution of work. It is difficult to manage all the construction works, but especially in the field of apartment construction work, complex and many kinds of works are being carried out at the same time. In the current construction, safety regulations such as safety management guidelines are generally well maintained, but the execution of manpower resources that can fulfill them is limited, and it is difficult to reduce the accident rate and loss cost. Therefore, in this study, it is a reality that most of the types of construction work are under contruction by subcontracting contract, so they are limit by methods of manual maintenance and safety education. Currently, the subcontractor is also allowed to perform safety management through the composition of the safety management review body, but it is operated formally. So alternatives to this were studied. As a result, safety accidents occur in the subcontractor's worker due to vertical integration, which is characteristic of the construction industry, together to the contractor, the safety management system is based on a safety construction system in which a worker who has a certain qualification condition such as career experience of the work type, work understanding of the work type, and management experience of the work type among the subcontractor, when we manage based on mutual personality which is the personality of interpersonal relationship that can communicate with each other by work type, process and grouping, it is concluded that effective and practical safety management can be achieved to reduce the accident rate and loss cost.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.461-465
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• 1996

Position and rate control modes arc the two common modes for controlling remote manipulators with joysticks or hand controllers. Generally, position mode is easier for teleoperation than rate modes, when the manipulation work space is small or comparable to the human operator's control space. When the telemanipulator's work space is very large, human operator's control motion range must be large to allow telemanipulator's full range of motion resulting poor control resolution. One way to solve the poor resolution problem is to use indexing. However, rate mode can provide any higher degree of resolution without use of indexing. If two modes are mixed, master controller will be more convenient. The mixed mode algorithm, changes operating mode from position mode to rate mode or vise versa using fuzzy logic. The fuzzy logic algorithm, which has been designed to recognize the teleoperator's intended motion properly, provides an intelligence to a master controller.

• 연구논문집
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• 통권29호
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• pp.49-55
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• 1999

Heat release rate used to characterize the fire is an important factor for determining the fire size, the fire growth and the time for suppression and evacuation. The purpose of present work is to review theoretical backgrounds and to introduce equations for estimation of heat release rate with oxygen consumption method in fires. Our work also shows the experimental results of applications for liquid fuels. The oxygen concentration is measured by the analyzer of paramagnetic type. The analyzers of Infra-Red type are used to measure the concentrations of $CO_2$ and CO gas. Time delays of analyzers are ignored.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.752-754
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• 1997

The stress intensity factor for an interface crack in dissimilar materials has been obtained by many researchers. But research of the energy release rate for an interface crack in pseudo-isotropic dissimilar materials is insufficient yet. In this paper, the energy release rate for cracks in pseudo-isotropic dissimilar materials was obtained using eigenfunction expansion method and also analyzed numerically using the reciprocal work contour integral method. The results were verified by comparing with other worker's results.