Dong-Choon Lee

A study on the prevention of accidents in subway station through the surveys on accidents in a subway station

This study analyzed the types of accidents that occur in a subway station in order to determine an effective means to prevent such accidents in the future. In addition, we examined potential railroad detection systems and compared them with the current subway operation system, including how the command center conducts its real-world evaluation of mishaps, the operators cabin and the operation of alarm systems. Based on the above studies, this paper aimed to develop a safety system that can promptly inform railroad operators and the command center of any mishap in order to secure the safety of passengers and conduct prompt computerized detection of emergency situations such as a fire or when a person or an object falls on the railroad in a subway station. Thus, this study helps to develop a safety system for emergency situations so as to protect precious human lives and to reduce processing costs or other economic costs entailed by delay or interruption of subway operation because of accidents

A Study on the Push and Pull Strength for the Design of Cart Handle

Objective: Product design process without considering the strength of the user can cause the excessive burden on musculoskeletal system of human body. Since the muscle strength will vary depending on the body posture, the design of product should consider the characteristics of body posture. This study was performed to investigate the effects of forearm postures on the push and pull strength. Background: Overexerted force has been identified to cause musculoskeletal disorders. It is important to know the push and pull strength exerted by human when designing so that exerted force does not exceed the safety limits. Method: Maximum isometric push and pull strength of left, right and both hands were measured according to forearm postures with pronation, neutral and supination. For the study, 66 male and 30 female undergraduate students were participated as subjects. All subjects were normal and healthy with no clinical history. Results: The results showed that the push strength of male and female were 93.3% and 85.4% of pull strength. It showed that the strength of one-hand was 72.1~81.0% of the strength of two-hands, and the strength of left hand was 93.1~95.8% of the strength of right hand. The strength of female was 62% of the one of male. It was found that the strength with pronation 90° was reduced up to 20% compared to the strength with neutral posture. Conclusion: Push and pull strength of male and female were reduced when forearm was rotated extremely. Application: The results of this study will be used for the prevention of work related musculoskeletal disorders and design of industrial equipment.

An Analysis of Transmitted-Vibration Characteristics by Different Wrist Posture during Grinding Tasks

This study was performed to evaluate the characteristics of transmitted vibration to hand-arm system under different work posture while operating a light-weighted powered hand grinder. For the experiment, 8 different types of wrist posture (natural, unlar-flexion, radual-flexion, flexion, extension, complex posture, and etc.) and 3 types of feed force (20[N], 50[N], 70[N]) were considered. 10 male subjects were employed to polish metal plate with a hand grinder. All of them were normal and healthy with no history and symptom of the work related musculoskeletal disorders in the dominant hand. Vibration acceleration data were recorded with sampling rate, 2048[Hz]. In addition, unweighted overall R.M.S. acceleration at the tool and wrist, and transmissibility between them were used to evaluate factors from the recorded tri-axial vibration acceleration. The results indicate that transmissibility of natural wrist posture was significantly higher than others. In addition, as the feed force becomes larger, the vibration was transmitted in large quantities to hand-arm system through radius.

An Analysis of Stress on Foot by Lifting Height and Angle

In this paper, we propose a stress analysis on foot by lifting task attitudes. Maximum force and peak pressure were measured on 8 body regions by Pedar system in order to analysis the stress which is affected by task style and angle on foot when Manual Materials Handling task. As for the peak pressure of the whole foot as to the task height during the lifting task, the height from Knuckle to Shoulder was the least in the peak pressure. Also, as for the maximum force and the peak pressure of the whole foot as to the task angle during the lifting task, it could be seen that the more an angle increases, the stress influencing on a foot jumps. As for the maximum force and the peak pressure by foot region as to the task height in case of the lifting task, the height from Knuckle to Shoulder is indicated the smallest value in the maximum force and the peak pressure, thus there is necessary to attain the work design that considered this. Also, as for the maximum force by foot region as to the task angle in case of the lifting task, 0° tasking is indicated to be least, thus there is necessity to be attained the tasking design in a bid to prevent the existence of an angle. The results of this paper are thought to be helpful to the suitable work design, to the prevention of musculoskeletal disorders related to the lower limbs, and to the design of ergonomic safety shoes.

A Study on Range of Joint Movement for Korean Adults

This study was performed to determine the voluntary range of movements for Korean adults at the age between 18 and 60. Three hundred and eighteen males and 260 females participated for this study. Twenty-seven body movements at various joints were conducted to measure the range of movements. Subjects were grouped by age into three to analyze the differences of range of movements due to the aging. The age ranged for the first group was from 18 to 29. The second group ranged from 30 to 39, and the last group ranged from 40 to 60. The data were also analyzed to see the differences of range of movements between sexes. The results show that female subjects have larger range of movements than male subjects in hip movement (hip adduction and abduction), knee movement (knee rotation medial and lateral), neck movement (right flexion, dorsal flexion, right rotation), wrist movement (wrist extension and adduction), elbow flexion and shoulder extension (p<0.05). On the other hand, male subjects have larger range of movements than female subjects in wrist abduction, wrist flexion, forearm supination, shoulder rotation (lateral), shoulder adduction, knee flexion (standing), ankle flexion, hip flexion, and hip rotation medial (sitting). (p<0.05). Generally, the range of movements decrease with ages, however, some range of joint movements such as wrist flexion and extension show increase with ages for both male and female subjects. To apply these data in designing products or workplace, the designers may need serious consideration to the limiting factor of incidence of arthritis due to the aging.