• Journal of Korea Society of Industrial Information Systems
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• v.5 no.1
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• pp.77-86
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• 2000

Even manual materials handling tasks(MMHT) is decreasing by adopt of automatic manufacturing system & transportation supporting machine because of increase of productivity, wage lack of labor, safety, in fact working at inclined & complicated slope such as farm, orchard, harbor loading & unloading, logging place and mining place can't be substituted by machine perfectly. So, workers should do MMHT at this place by themselves, lifting on slope can cause much of hazard, include falling. Keeping balance net to slip can be a reason of low back pain(LBP) by overloaded musculoskeletal system but, there's no enough study about lift on slope. Therefore, In this study, we assessed and analyzed change of center of pressure(COP) when lifting on slope by force platform. The result showed that the length lengthen as increasing angle of slope. Especially, the length extremely increased over 15°. Through These basic result, present proper angle boundary, prevent industrial accidents and give proper data not only lifting but also pushing and pulling on slope someday.

• Journal of agricultural medicine and community health
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• v.44 no.3
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• pp.138-143
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• 2019

Objectives: The purpose of this study was to assess the ergonomic risk factors in beekeeping, and to evaluate the effectiveness of assistive device hive lift. Methods: This study included 30 subjects of beekeeper in Pocheon, Korea. We assessed the ergonomic risk of main task in beekeeping with NLE, OWAS and evaluate the effectiveness of hive lift. We also surveyed prevalence of musculoskeletal symptoms among the subjects based on the Korea Working Condition Survey. Results: Moving to different floral origin, internal inspection of beehives, feeding syrup is the most burdensome to musculoskeletal system (NLE LI value=2~3. OWAS action category=4). The prevalence of musculoskeletal symptoms (lower and upper extremities) among the subjects was over 80 %. The introduction of assistive devices in the three hazardous tasks has dramatically reduced the risk by removing manual lifting hives (OWAS action category<1). Conclusions: Beekeeping is a heavy workload on the musculoskeletal system because it has a lot of manual lifting task. As a result of applying the hive lift, the burden could be reduced.

• Journal of the Ergonomics Society of Korea
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• v.19 no.2
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• pp.87-99
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• 2000

This study aims to examine a fuzzy logic-based human expert EMG prediction model (FLHEPM) for predicting electromyographic responses of trunk muscles due to manual lifting based on two task (control) variables. The FLHEPM utilizes two variables as inputs and ten muscle activities as outputs. As the results, the lifting task variables could be represented with the fuzzy membership functions. This provides flexibility to combine different scales of model variables in order to design the EMG prediction system. In model development, it was possible to generate the initial fuzzy rules using the neural network, but not all the rules were appropriate (87% correct ratio). With regard to the model precision, the EMG signals could be predicted with reasonable accuracy that the model shows mean absolute error of 8.43% ranging from 4.97% to 13.16% and mean absolute difference of 6.4% ranging from 2.88% to 11.59%. However, the model prediction accuracy is limited by use of only two task variables which were available for this study (out of five proposed task variables). Ultimately, the neuro-fuzzy approach utilizing all five variables to predict either the EMG activities or the spinal loading due to dynamic lifting tasks should be developed.

• Journal of the Korean Society of Safety
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• v.29 no.4
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• pp.153-159
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• 2014

Low back pain is one of major issues in musculoskeletal diseases mainly caused by MMH (Manual Material Handling) tasks. In Korea, the standards of NIOSH(National Institute for Occupational Safety and Health) Lift Equations in U. S. A. have been most widely used. However, there is no standard in case the height of one feet is higher than that of another one. Moreover, since the standards are developed in U. S. A., there are many limitations for the applicability of Korean workers. In this study, MVC(Maximum Voluntary Contraction) for four postures are measured and an empirical model based on SVR(Support Vector Regression) is constructed. Constructing SVR model, PSO(Particle Swarm Optimization) is employed to investigate the optimal parameters of SVR. The results show that the performance of this empirical model is approximately accurate, even if the deviation of experimental values is large due to the individual differences. This empirical model may contribute to establish the standards of MMH tasks in Korea.

• Journal of the Ergonomics Society of Korea
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• v.27 no.1
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• pp.45-51
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• 2008

The purpose of this survey was to identify ergonomic risk factors of work-related musculoskeletal disorders (MSD) and understand the current MSD risk status in the wholesale/retail industry. The field survey was conducted at 120 wholesale/retail establishments, and the cause of MSD occurred from the national industrial accident statistics by the Ministry of Labor in 2006 was analyzed in terms of company size, a term of work, job title, and cause of occurrence. The numbers of disasters on MSD were 602 which were included 432 disasters who met with low back pain by incident. A checklist was developed by KOSHA to use for the field survey. A total of 419 tasks were identified at the 120 establishments surveyed. The highest frequency was Task 2(45%) which was mostly observed in repetitive work (e.g. displaying, scanning, cutting or wrapping of goods). The second and third were Task 9(34%) and Task 8(14%) which were identified in manual materials handling (e.g. lifting, lowering, carrying or stocking of goods). The results suggest that the three Tasks should be first considered for the control in wholesale/retail industry and that exposure to MSD risk factors in those Tasks should be primarily addressed in order to reduce MSD risk in that industry.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.124-133
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• 2017

In the current lighting market, LEDs that have a high luminous efficiency, a long life and consume less power have emerged as next generation lighting. Owing to various designs and sizes of LEDs, the production process of existing LEDs involves many tasks that require manual labor; hence, the assembly of LEDs necessitates manpower. Because of the use of manpower, the production costs of LEDs increases and production efficiency decreases. Recently, the assembly parts of LEDs have been standardized for minimizing manual labor, and an LED is developed as an LED panel. The automatic assembly system produces LED convergent lighting by assembling two LED panels and one diffusion cover. To increase the production efficiency of the LED convergent lighting module, it is important that the development of a feeder can continuously supply the LED panels is required, and whose design has sufficient stability. The automatic assembly system of the LED convergent lighting module consists of two feeders, which convey LED panels and diffusion covers to a main conveyor, which assembles the lifted panels and covers. In this study, structural analysis and fatigue life for forced loads on the conveyer line of the feeder in the process of lifting LED panels and diffusion covers of each feeder, is analyzed. In addition, the drive of the belt constituting the conveyor line of each feeder is simulated, and the dynamic characteristics of the belt is analyzed using the virtual engineering method.

• Journal of the Korean Society of Safety
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• v.26 no.3
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• pp.69-74
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• 2011

Despite most of tasks in manufacturing, construction and agriculture, etc., were currently mechanized and automated, manual materials handling still existed in atypical working condition. In case of manual materials handling, repetitive work, inappropriate working posture, excessive force, contact stress might cause overload, which could lead to work-related musculoskeletal disorders and low back pains. On this basis, the goal of this study is to reveal the effects of various lifting postures of trunk angles and lower extremity postures on maximum holding time(MHT). Twenty two subjects were recruited from a university population. The experiment was designed by a combination of three trunk angle ($0^{\circ}$, $20^{\circ}$, $60^{\circ}$) and three lower extremity postures(straight, bent, kneeling). Before experimental trials, subjects performed MVC(maximum voluntary contraction) exertions in three trunk angles ($0^{\circ}$, $20^{\circ}$, $60^{\circ}$) to calculate 30%MVC at designated postures. In each trial, they were required to hold the handheld load(30%MVC) for a designated posture as long as they could. The results of MVC by trunk angles were measured in $0^{\circ}$ > $20^{\circ}$ > $60^{\circ}$ orders, but those of MHT measured in $20^{\circ}$ > $0^{\circ}$ > $60^{\circ}$ orders. These results showed that straight posture is the ideal working posture in work exerted a strong force for a short time, but the ability to work might be improved in the trunk angle $20^{\circ}$ in work required 30%MVC for a long time. Also, results of MVC and MHT by lower extremity postures measured in straight > bent > kneeling orders.

• Journal of the Ergonomics Society of Korea
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• v.34 no.1
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• pp.1-10
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• 2015

Objective: The purpose of this paper is to evaluate old and newly designed ammunition boxes from an ergonomic point of view. Background: The ammunition boxes made of wood, which are currently used by the military, have some difficulties such as corrosion and damage of ammunition, environmental pollution, and stock management. Also, damages to the wooden ammunition boxes take place frequently, because soldiers carry them manually. Method: Sixteen participants volunteered to randomly perform lifting, carrying, and side-by-side moving tasks with 4 different old and new boxes, respectively for the ammunitions of 5.56mm, 60mm, 81mm, and 105mm in diameter. The old boxes are made of wood and are currently used in the military, while the new boxes are made of plastics. The joint moments of the elbow, shoulder, back, and knee were measured by using a motion analysis system and force platforms. In addition, an electromyographic system was used to measure the forces of hand and wrist muscles. Results: In most tasks, new boxes caused less joint moments at the elbow and shoulder than old boxes, because the new boxes were lighter and smaller than the old boxes. New boxes also derived less hand and wrist muscle forces due to the provision of fixed hard handles rather than string handles. Conclusion: The ergonomically designed new boxes could reduce the physical stresses of soldiers manually handling ammunitions and be helpful for storage and reuse. Application: This study shows an ergonomic application example for product development and evaluation.

• Journal of the Ergonomics Society of Korea
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• v.34 no.3
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• pp.279-291
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• 2015

Objective: The purpose of the study is to evaluate appropriate weight for aged farmers in manually handling livestock feed in bags using ergonomic methods. Background: In the livestock industry in South Korea, despite the trend of aging of labor manpower, heavy items are still manually handled in many farms. In particular, among stockbreeding works, the handling of feed in bags weighing 25~30kg is reported as a cause of frequent injuries and musculoskeletal system diseases. However, studies on the standard for recommended weight allowed considering the physical characteristics of aged farmers older than 60 years with greatly decreased physical strength and muscle strength are insufficient. Method: To evaluate appropriate weight for handling of heavy livestock feed in bags, physical techniques for measuring recognized levels of physical work loads, the NLE (NIOSH lifting equation) a method that is an observation type technique, and an ergonomic modeling technique to predict compressive force imposed on L5/S1 were used. Subjects who participated in the experiment were organized into two groups of males/females with mean age exceeding 60 years, and lifting tasks were evaluated for nine weight levels. Results: Based on the results of psychophysical measurement, females showed a tendency of more drastic increases compared to males when weight was over 19kg. The results of estimation of regression models for the weight, 18.0 kg ($r^2=0.97$) and 15.3kg ($r^2=0.97$) were evaluated as stable load for males and females, respectively. In addition, both the observation type evaluation and ergonomic model evaluation showed stable loads in a range of 15~18kg. Conclusion: Given the results of the study, the weight of the feed in bags currently distributed to farms can become a cause of not only overexertion but also farm work related disasters such as musculoskeletal disorders and safety accidents. Providing livestock feed in bags weighing not more than 19kg for aged farmers is judged desirable, and managerial improvement for this matter is considered necessary. Application: The results of the present study can be utilized as useful data for institutional improvement of the weight of livestock feed in bags.