Usability evaluation of augmented reality visualizations on an optical see-through head-mounted display for assisting machine operations.

This study explores the effect of using different visual information overlays and guiding arrows on a machine operation task with an optical see-through head-mounted display (OST-HMD). Thirty-four participants were recruited in the experiment. The independent variables included visual information mode (text, animation, and mixed text and animation) and the use of guiding arrows (with and without arrows). In addition, gender difference was also an objective of this study. The task performance indicators were determined based on task completion time and error counts as well as subjective measures (system usability scale, NASA task load index, and immersion scale). This study used the mixed analysis of variance design to evaluate the main and interaction effects. The results showed that males performed better when using the mixed text and animation mode. Females performed better when using the text mode. In addition, using the mixed text and animation mode demonstrated the best outcome in system usability scale and NASA task load index. For the use of guiding arrows, the task completion time was reduced and the system usability scale, NASA task load index, and immersion scale showed positive effects.

Usability evaluation of an instructional application based on Google Glass for mobile phone disassembly tasks.

This study aims at comparing a Google Glass-based instructional application with a printed manual in mobile phone disassembly tasks. Thirty participants (15 males and 15 females) were recruited to perform tasks via three types of instructional methods (Google Glass-based augmented reality, Google Glass-based video, and a printed manual). The objective measures of performance (task completion time, error counts), and the subjective measures (NASA-Task Load Index, system usability scale) were considered. Additionally, visual fatigue was assessed by critical flicker fusion frequency and near point accommodation. According to the findings, although the printed manual method produced better results regarding mental workload and system usability, the augmented reality method improved error reduction and efficiency. Furthermore, the participants indicated that the displayed animations were helpful in locating the exact work-pieces. The augmented reality method is believed to be a potential alternative to printed manuals in mobile disassembly tasks.

EFFECTIVE INDICES FOR MONITORING MENTAL WORKLOAD WHILE PERFORMING MULTIPLE TASKS.

This study identified several physiological indices that can accurately monitor mental workload while participants performed multiple tasks with the strategy of maintaining stable performance and maximizing accuracy. Thirty male participants completed three 10-min. simulated multitasks: MATB (Multi-Attribute Task Battery) with three workload levels. Twenty-five commonly used mental workload measures were collected, including heart rate, 12 HRV (heart rate variability), 10 EEG (electroencephalography) indices (α, ß, θ, α/θ, θ/ß from O1-O2 and F4-C4), and two subjective measures. Analyses of index sensitivity showed that two EEG indices, θ and α/θ (F4-C4), one time-domain HRV-SDNN (standard deviation of inter-beat intervals), and four frequency-domain HRV: VLF (very low frequency), LF (low frequency), %HF (percentage of high frequency), and LF/HF were sensitive to differentiate high workload. EEG α/θ (F4-C4) and LF/HF were most effective for monitoring high mental workload. LF/HF showed the highest correlations with other physiological indices. EEG α/θ (F4-C4) showed strong correlations with subjective measures across different mental workload levels. Operation strategy would affect the sensitivity of EEG α (F4-C4) and HF.

Comparing 3D foot scanning with conventional measurement methods.

BACKGROUND: Foot dimension information on different user groups is important for footwear design and clinical applications. Foot dimension data collected using different measurement methods presents accuracy problems. This study compared the precision and accuracy of the 3D foot scanning method with conventional foot dimension measurement methods including the digital caliper, ink footprint and digital footprint. METHODS: Six commonly used foot dimensions, i.e. foot length, ball of foot length, outside ball of foot length, foot breadth diagonal, foot breadth horizontal and heel breadth were measured from 130 males and females using four foot measurement methods. Two-way ANOVA was performed to evaluate the sex and method effect on the measured foot dimensions. In addition, the mean absolute difference values and intra-class correlation coefficients (ICCs) were used for precision and accuracy evaluation. The results were also compared with the ISO 20685 criteria. RESULTS: The participant's sex and the measurement method were found (p < 0.05) to exert significant effects on the measured six foot dimensions. The precision of the 3D scanning measurement method with mean absolute difference values between 0.73 to 1.50 mm showed the best performance among the four measurement methods. The 3D scanning measurements showed better measurement accuracy performance than the other methods (mean absolute difference was 0.6 to 4.3 mm), except for measuring outside ball of foot length and foot breadth horizontal. The ICCs for all six foot dimension measurements among the four measurement methods were within the 0.61 to 0.98 range. CONCLUSIONS: Overall, the 3D foot scanner is recommended for collecting foot anthropometric data because it has relatively higher precision, accuracy and robustness. This finding suggests that when comparing foot anthropometric data among different references, it is important to consider the differences caused by the different measurement methods.

The effect of air permeability and water vapor permeability of cleanroom clothing on physiological responses and wear comfort.

The function of cleanroom clothing is to protect the product from contamination by people, and to dissipate electrostatic discharge. People in the cleanroom work environment often complain about the discomforts associated with the wearing of cleanroom clothing. The purpose of this study is to investigate the effect of air permeability and water vapor permeability of cleanroom clothing on the subject's physiological and subjective responses. Five male and five female subjects participated in this study. The experimental goal was to simulate the operator's regular tasks in a semiconductor manufacturing cleanroom. Each subject completed three treatment combinations with three different cleanroom clothing types. A three-factor experiment was designed (significance level p = 0.05). The independent variables included gender, cleanroom clothing, and duration. The dependent measures included heart rate, core temperature, skin temperature, micro-climate relative humidity, micro-climate temperature, and subjective responses. A total of 40 min was involved for each treatment condition. The results indicate that skin temperature, micro-climate temperature and micro-climate relative humidity were lower while wearing cleanroom clothing with high air permeability and high water vapor permeability. The significant gender difference was found in skin temperature. As the task time increased, the micro-climate temperature also increased but the micro-climate relative humidity decreased at first and then increased. In addition, the physiological responses showed significant positive correlations with the subjective perception of clothing comfort. The findings of this study may provide useful information for cleanroom clothing design and selection.

Evaluating the effectiveness of using electroencephalogram power indices to measure visual fatigue.

Electroencephalography (EEG) is widely used in cognitive and behavioral research. This study evaluates the effectiveness of using the EEG power index to measure visual fatigue. Three common visual fatigue measures, critical-flicker fusion (CFF), near-point accommodation (NPA), and subjective eye-fatigue rating, were used for comparison. The study participants were 20 men with a mean age of 20.4 yr. (SD = 1.5). The experimental task was a car-racing video game. Results indicated that the EEG power indices were valid as a visual fatigue measure and the sensitivity of the objective measures (CFF and EEG power index) was higher than the subjective measure. The EEG beta and EEG alpha were effective for measuring visual fatigue in short- and long-duration tasks, respectively. EEG beta/alpha were the most effective power indexes for the visual fatigue measure.

Evaluating insole design with joint motion, plantar pressure and rating of perceived exertion measures.

This study compared a newly-designed insole with two commercially available insoles. The response measures included joint motion, plantar pressure and rating of perceived exertion. Thirty healthy female students were paid to participate in this study. The results showed that significant differences among the three insoles were found in plantar pressure and rating of perceived exertion. There were no significant differences among three different insoles in join motion measures. When wearing the newly-designed insole, the plantar pressure under heel area would transfer to midfoot area, and resulted in lower subjective discomfort ratings in midfoot and heel areas. The barefoot condition showed the worst performances in most of the response measures. The findings of this study provide very useful information for ergonomic insole design.

Approach strategy and working posture in manual hand tool operation.

The strategy for approaching a manual work position is an important reference for describing a goal-directed task. However, knowledge on this aspect of human behavior is scarce. The objectives of this study are twofold: (1) to describe and understand the strategy people tend to adopt for approaching a manual work position from different directions when their initial standing position is three meters away, and (2) to describe the working posture they tend to adopt when operating a pistol-grip hand tool at different heights. An experiment involving eight participants was conducted to measure the whole-body position and orientation when approaching a work position from five directions. The working posture adopted when operating a pistol-grip hand tool at six working heights was examined. The results indicate that the final whole-body position and orientation (while performing the operation) was affected significantly by the approach direction. A linear relationship between the approach direction and the final whole-body orientation was obtained. The participants adopted a strategy combining the work efficiency and comfort strategies. They deviated from the least-distance (straight line) walking path and re-oriented their whole body for the operation when approaching the work position. The working posture was significantly affected by the working height. The working postures at six working heights were established. The participants adopted a standing posture when the working height was between eye and hip height, and a stooping or squatting posture when operating at knee and ankle height. The results of this study can be used to enhance digital human modeling motion generated for human movement simulation.

The evaluation of force exertions and muscle activities when operating a manual guided vehicle.

A manual guided vehicle (MGV) is used to handle heavy materials in thin film transistor-liquid crystal display (TFT-LCD) manufacturing clean rooms. This study focuses on evaluating the force exertions and muscle activities in MGV operations. The independent variables include gender, force direction, handle height, load handled and wheel diameter of the MGV. The results show the force direction, handle height and load handling effects are significant in most measures except for F(ending) (the peak force required to stop the MGV) and the EMG of the anterior deltoid. The wheel diameter had a significant effect on F(initial) (the peak force required to move the MGV) and F(ending) responses. Gender did not significantly effect any measures. Moreover, the pushing and pulling force is less at 115cm handle height than at 101.5cm and 88cm handle heights. Using 15.3cm (6 inch) diameter wheels requires less force than 20.3cm (8 inch) diameter wheels because the two front wheels are fixed and the two rear wheels are rotatable. The design implications are discussed.

The effect of arm posture on the scan-derived measurements.

Among various three-dimensional (3D) scanning anthropometric surveys, the inconsistent arm postures for scanning may lead to incompatible measurement results. Therefore, this study aims to investigate the effect of arm posture on the scan-derived measurements. The two arm postures in concern are the one with palms facing inward and the one with palms facing backward. The experimental results reveal that the two postures do not differ from each other in obtaining the scan-derived measurements for most body dimensions except for those related to the upper torso. Besides, the scan-derived measurements can be more precise between the two postures than the manual measurements. Further, it was found that being scanned with palms facing backward can contribute to the smaller difference between the scan-derived measurements and the manual measurements and the better image quality. Overall, the arm posture with palms facing backward is considered as the preferred posture for 3D whole body scanning.

The change of gait parameters during walking at different percentage of preferred walking speed for healthy adults aged 20-60 years.

This study aims to investigate the effects of age, gender and walking speed on the gait performance during walking at a range of percentage of preferred walking speed (PPWS). The subjects were aged from 20 to 60 years and both genders were equally represented. A nested-factorial analysis of variance was employed. The independent variables include walking speed (80%, 100%, 120%, and 140% PPWS), age (young, middle, and older groups) and gender. The response measures include lower limb joint motion, vertical ground reaction force (VGRF), muscle electromyography (EMG), heart rate, and perceived exertion of whole body and local areas. The results show that different age and gender groups had similar gait performance on most of the joint motions, HR, as well as the perceived exertions while walking at a range of PPWS. In addition, these performance generally increased with the increasing walking speed and the trend becomes more obvious when the speed was higher than 120% PWS. Age and gender differences have been found in VGRFs and muscle EMG. Females exhibited significantly higher VGRF in the heel-strike and toe-off stages, as well as higher tibialis anterior muscle activity. Older subjects had significantly higher rectus femoris muscle activity than younger adults. Besides, the interaction between gender and walking speed was significant on VGRF in the toe-off stage. Further discussions are addressed.

Evaluating work ability and quality of life for clinical nurses in Taiwan.

This study investigated the work ability and its relationship with quality of life for the clinical nurses in Taiwan. The survey was of 1534 nursing professionals from 8 different hospitals. Work ability of nursing professionals varied by age, work experience, working departments and hospital types. Work ability of nurses increased with age until after the age of 45. Personal health condition and physical workload were the main factors contributing to the decline of the perceived work ability for senior nurses. For young nurses, the mental demands of work were a critical influence on their work ability. Moreover, work ability of nurses varied among hospital type and department. The work ability of nurses was strongly associated with the quality and safety of the work environment and leisure time management. For improving and maintaining the work ability of nurses, countermeasures such as enhancing the ability to cope with the job's mental demands for young nurses, and improving the job design to reduce physical workload for senior nurses are recommended.

Biomechanical, physiological and psychophysical evaluations of clean room boots.

The purpose of this study was to evaluate the significance of boot sole properties on reducing fatigue, to evaluate the effects of load carrying and walking (over a 1 h period) on biomechanical, physiological and psychophysical responses, and to investigate the correlations between the measurements. The results indicated that elasticity and shock absorption of the boot had significant effects on outcome variables. Significant load effects were seen in most measurements. All of the significant time period effects gave strong regressions, with no R2 value less than 0.983. The findings of this study provide useful information for the selection and design of clean room boots as well as for job design for load carrying tasks in the clean room environment.

Professional footwear evaluation for clinical nurses.

Epidemiological investigations indicate that nursing professionals experience a higher prevalence of musculoskeletal disorders (MSDs) than most other occupational groups. Most nursing activities require standing and walking for prolonged periods. Such job requirements may contribute to MSD problems in the lower extremities. Thus, wearing comfortable nursing shoes is essential to reduce the lower-extremity discomfort for clinical nurses. The objectives of this study are: (1) to evaluate three brands of commercially available nursing footwear and identify the important shoe features for adequate shoe support during nursing activities, and (2) to assess the effect of wearing compression hosiery by measuring the biomechanical, physiological, and psychophysical responses of test participants. The method of this study involved two phases. First, field observations were conducted to collect job demand data, including walking speed, and the ratios of walking, standing, and sitting. Second, an experiment was conducted to evaluate the functions of professional nursing footwear and examine the influence of compression hosiery on lower extremity discomfort relief. Measurements included electromyography (EMG) of the lower leg, joint range of motion (ROM) in the lower extremity, foot pressure, ground reaction force (GRF), and subjective discomfort ratings for the lower body and feet. Summarizing the findings of this study, comfortable footwear for nursing professionals should emphasize a footbed with arch support outside with 1.5 cm thickness of EVA materials in the metatarsal zone and heel height between 1.8 and 3.6 cm; this can minimize foot pressure distribution, impact force, and increase shin and ankle comfort. In addition, wearing compression hosiery is recommended to alleviate lower body and foot discomfort for clinical nurses.

Torque levels, subjective discomfort, and muscle activity associated with four commercially available screwdrivers under static and dynamic work conditions.

This study evaluated screwdrivers with different handle designs and blade lengths. 10 men and 10 women voluntarily participated. A repeated-measures experiment design was employed. The three independent factors were sex of user, handle (four types), and blade length (130, 170, and 210 mm). The dependent measures were the maximum supination torque under a static task and the %MVC of EMG responses in biceps brachii and flexor digitorum, and a discomfort rating for the upper extremity under the dynamic task. Analysis showed that the in-line screwdriver with the combined characteristics of large handle diameter (3.8-4.1 cm), smooth rubber covering handle surface, triangular (or circular) shape, and adequate handle length (11 cm) had the greatest supination torque and a smaller discomfort rating than the screwdriver with the pistol-grip handle. Blade length was not significantly related to any dependent measure.

The comparisons of anthropometric characteristics among four peoples in East Asia.

This study presents comparisons of ethnic difference in anthropometric characteristics among four peoples, i.e., Chinese, Japanese, Korean, and Taiwanese, in East Asia. Anthropometric data from the four East Asian countries were compared. The means of 33 body dimensions and 31 bodily proportions are presented. Also, 15 segmental proportions are illustrated. The results of statistical analyses showed that there is a significant morphological difference among these peoples in the same region. The Mainland Chinese body shape has a narrower body with mid-range limbs. The Japanese body shape is wider with shorter limbs. The Korean body shape is mid-range among the four peoples, but the upper limbs are longer. The Taiwanese body shape has wide shoulder and narrow hip with large hands and long legs. The ethnic diversity in bodily proportions should be considered as well as the mean dimensions.

Relationship between maximum acceptable work time and physical workload.

For safe job design, it is necessary to know the maximum acceptable work time (MAWT) for a given workload. The aim was to establish the relationship between MAWT and physical workload. Cycling tests at six different work rates relative to personal maximum working capacity were performed by 12 young adults in the laboratory. The oxygen uptake (VO(2)) in the per cent maximum aerobic capacity (%VO(2max)), relative heart rate (RHR) and relative oxygen uptake (RVO(2)) were collected throughout the test. MAWT was determined by observing the heart rate data during the test. The results showed that MAWT was negatively correlated with %VO(2max), RHR and RVO(2) (p < 0.01). Three exponential regression models were obtained and all their R(2) > 0.80. These models suggest that long-hour shifts (> 10 h) should assign a lower work intensity than for an 8-h workday. It is also logical that the workload limit for a 4-h work shift could be set at about 10% VO(2max) higher than the suggested limit for an 8-h workday.