A new design of shoulder straps and frame of backpack is proposed for reducing compression and fatigue of shoulder. The stress reduction effects of a backpack equipped with the newly designed shoulder straps and frame have been analyzed statistically through various experiments. We show that the newly designed shoulder straps(wider than the conventional ones) is superior to existing shoulder straps in respect of RPE, task performance measure and physiological measure. The new frame is also proven to be superior to existing frame in respect of RPE and task performance measure. In conclusion, the proposed shoulder straps and frame are shown to enhance the task performance of soldiers.

The purpose of this study is to quantitatively investigate perceived discomfort of complex shoulder postures with external loads and to propose a preliminary evaluation scheme of shoulder postures. Twelve healthy male adults participated in an experiment to rate their perceived discomfort of shoulder postures. The independent variables were shoulder flexion angle(45, 90 and 150$^{\circ}$), adduction/abduction angle(-30, -10, 0, 30 and 60$^{\circ}$), and external load(0, 1.5 and 3.0kg). The results revealed that the flexion angle, external load and their interaction significantly affected the perceived discomfort(p$<$0.05) but the effect of adduction/abduction angle on the discomfort was not significant(p$>$0.05). The effect of external load was much larger than that of any other factor with explaining about 81% of the total variation of discomfort scores. Based on the experimental results a preliminary scheme was presented to evaluate the stress of shoulder postures with external loads.

The objective of this study is to examine the prevalence of musculoskeletal disorders(MSDs) among nursing personnels. A self-reporting survey adapted from Nordic questionnaires was used as diagnostic tool, and conducted for 162 nurses working for a general hospital. The survey was performed five times every three months during a year. The MSDs were defined by using three criteria, depending upon the frequency, duration and pain intensity of the symptoms. The results showed that the 12-month prevalences of MSDs at any body site by criterion 1, 2, 3 were 56.8%, 53.7%, 45.7%, respectively, and that the shoulder was the most susceptible to MSDs, followed by knee/lower leg, lower back, hand/wrist, neck, ankle/feet, finger, etc. Only one statistically significant risk factor of departments or units was identified through the Chi-square test. The prevalence of MSDs was the highest in intensive care unit, second in surgical ward, while the prevalence was the lowest in emergency room. The MSDs prevalence of Korea at any body part or by body part was much lower than that of foreign countries such as Japan, USA, Sweden, etc. This implies that when considering poor working conditions and load in Korea, the incidence rate of MSDs may rapidly increase in Korea in the future.

In order to minimize a biased view of evaluators in usability test, a multiple evaluation method so called Multi-Centered Usability Evaluation Method(MCUEM) was suggested and structured in this study. To use MCUEM, the existing evaluation methods were re-categorized into 'developer and evaluator-centered', 'evaluator-centered', 'user-centered', 'evaluator and user-centered', and the 'developer, evaluator, and user-centered methods. Furthermore, in order to verify the relevance of MCUEM, the usability of mobile phone was tested in this study. In results, it was found that different evaluation methods generated greatly different results, that showed the risk of using a particular usability method due to different perspectives of evaluators. At the same time, it was found that MCUEM could greatly minimize such biases. Therefore, it was concluded that using MCUEM could help the usability engineer design a test protocol with a minimal risk of bias due to different perspective of evaluators.

The purpose of this study is to suggest computer assisted neck-base's landmark identification algorithms and measurement extraction methods from three-dimensional human scan data. So we developed the algorithms for automatic identification of landmarks related to the neck-base types. The subjects were 58 women $18{\sim}24$ years of age. Their body were measured directly and indirectly by using camera and three-dimensional body scanner. They were measured during the months of October in 2001. Based on the characters of classified neck-base types, algorithms for the automatic identification of landmarks and methods of automatic measurement are developed. The three-dimensional automatic measuring program is made by $C^{++}$ language. Using this program, 4 landmarks are identified and 6 items are measured. In the verifying the precision of automatic measurement, the height measurements(cervicale, side neck point, front neck point) were relatively accurate, but neck-base width measurement was measured wide.

The FSA(Force Sensitive Application) system measures hand force by using force resistance sensors. Compared to conventional hand force measurement systems such as Lafayette hand dynamometer and Jamar hydraulic hand dynamometer, the FSA system can be applied to analyze use of hand forces while the hand is manipulating objects for a task, However, the measurement performance of the FSA system has not been objectively evaluated. The present study tested the FSA system in terms of stability, repeatability, accuracy, and linearity. It is shown that the FSA system has good stability (CV$\leq$0.02) and linearity($R^2$=0.82), but has low repeatability(CV=$0.11{\sim}0.19$) and accuracy(22% of underevaluation on average). This performance result indicates that measurements from the FSA system should be used for relative comparison rather than for absolute comparison.

Human perceptional speed is different from its real speed. There is lack of research that the perceptional speed is different from real speed in 2-dimension, because most research of speed perception has concentrated on points and lines. This research investigates the effects of object size on speed perception. In this research, we used 2-D circular objects of the different size, 0.9, 1.8 and $3.6^{\circ}$. The objects moved 9.0, 13.5 and $18.0^{\circ}$ with three different speeds, 6.0, 9.0 and $18.0^{\circ}$/s. Six participants were exposed to the environment with standard scene(size: $1.8^{\circ}$, speed: $9.0^{\circ}$/s and travel distance: $13.5^{\circ}$). After the first scene, another scene in which the object had changed to different sizes, speeds and distances, was shown to the participants. A magnitude estimation method was used to construct a scale of the perceived speed level. The relationship between the perceived and the actual speed level was explained by Stevens's power law that the value was 0.978 with the exponent of 0.992. The size of object had an effect on the speed perception but travel distance was not. The perceptional speed of bigger object was lower than of smaller object. It showed that the degrees of perceptional speed decreased as size of object increased.

Ergonomic intervention techniques were adopted to assess and control potential risk factors of work-related musculoskeletal disorders(WMSDs) in the automated light assembly manufacturing system. Ten different kinds of assembly workstations implemented with a conveyor system and twelve female workers were observed and evaluated with careful video film analysis. Several close examinations using sets of checklists established by qualified safety and health organizations, such as NIOSH, OSHA, and ANSI, were conducted and every workers and staffs in the site participated in the self-report questionnaires and off-line interviews. Typical risk factors and symptoms of the upper extremity musculoskeletal disorders were found and categorized into specific parts of body. To reduce risk factors of WMSDs and improve system productivity new revised workstation standards, physical dimensions, were suggested accordant with anthropometric characteristics of workers and a heuristic decision strategy of rotating shift work schedules according to work contents has proposed to mitigate cumulative physical stress. Finally, ergonomic programs of entire company to prevent WMSDs were structured.

Evaluation of repetitiveness for upper extremity intensive tasks is essential to determine the level of risk for upper extremity musculoskeletal disorders at the workplace. However, experimental data available to establish the acceptable levels of repetitiveness for various postures and forces is lacking. The present study examined the maximum acceptable frequencies(MAFs; motions/min.) of shoulder, elbow, wrist, and index finger motions at different forces(1kgf and 4kgf for shoulder, elbow, and wrist; 0.25kgf and 1 kgf for index finger) in sitting. Seventeen right-handed males in 20s without having any history musculoskeletal disorders participated in the MAF experiment. The participants determined their MAFs for the upper extremity motions by using the self-adjustment method and their work pulse(increase in heart rate; beats/min.) and rating of perceived exertion(RPE) were measured when working at MAF. The MAFs of elbow, wrist, and index finger motions for each force level were about 2, 3, and 6 times the corresponding MAF(9 at the high force and 24 at the low force) of shoulder motion and the MAFs at the low force increased about 2 times those at the high force. The work pulses of elbow, wrist, and index finger motions for each force level were 70%, 50%, and 30% of the corresponding work pulse(17 at the high force and 12 at the low force) of shoulder motion and the work pulses at the low force were about 70 % of those at the high force. Lastly, the RPEs of the upper extremity regions were about level 3(moderate) or below.

In spite of the importance of nuclear power as one of major electric energies in Korea, the nuclear safety has become the most serious social issue in the operation of the nuclear power plant. In this paper, a virtual work simulation program was developed to predict exposure dose during radiation work in radwaste storage. The work simulation program was developed. using $Java ^{TM}$applet and VRML-virtual reality modeling language. A numerical algorithm to find the optimal work path which minimize exposure dose during the given work, was developed and exposure dose on the optimal work path was compared with that on the shortest path. Comparing with the shortest path for the given work, the predicted optimal path consumed longer work time by II% but reduced total exposure dose by 46%. The simulation result showed that the exposure dose depended on not only work time, but also the distance between the worker and the radiation source. The developed simulation program could be a useful tool for the planning of radioactive waste work to increase the radiation safety of workers.

In order to verify the effects of sleep efficiency and sleep latency depending on the sound, Polysomnography was carried for the different sound stimulations, such as Sound A(providing R bed Co.), Sound B(1/f fluctuation sound develope by KRISS), and no sound stimulation. In case of sleep efficiency and WASO(wake after sleep onset) ratio Sound B shows more affirmative effect than no sound stimulation or Sound B. It is the result that the effect is caused because 1/f fluctuation sound has the rule and unexpectation. This research results show the possibility of application and development of the sound for sleep.

To understand the basic relationship between 3D curved surface model and 2D pattern, simplified torso model was generated by commercial CAD program (IDEAS). 3D torso model was then divided into different blocks and unfolded into a flat pattern as in ordinary works of clothing item design. As results, 2D pattern development of different part of 3D torso model was attempted and analyzed mathematically. It was found that different height, radius and tangent slope of 3D blocks resulted in different 2D pattern. The relationships between the shape parameters of 3D torso blocks and those of 2D patterns were analyzed using regression equations. Direct way of drawing a 2D pattern of corresponding 3D torso block was also illustrated for the convenience of pattern making using conventional measurements of upper/ lower radii and height of 3D torso block.