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.

Determining Work-Rest Schedules for Visual Tasks That Use Optical Head-Mounted Displays Based on Visual Fatigue and Visually Induced Motion Sickness Recovery.

This study aimed to determine work-rest schedules for visual tasks of different lengths by evaluating visual fatigue and visually induced motion sickness (VIMS) using an optical head-mounted display (OHMD). Thirty participants were recruited to perform 15 and 30 min visual tasks using an OHMD. After completing each visual task, participants executed six levels of rest time. Critical flicker fusion frequency (CFF) values, relative electroencephalography indices, and Simulator Sickness Questionnaire (SSQ) scores were collected and analyzed. Results indicated that after completing the 15 and 30 min visual tasks, participants experienced visual fatigue and VIMS. There was no significant difference between baseline CFF values, four electroencephalography relative power index values, and SSQ scores when participants completed a 15 min visual task followed by a 20 min rest and a 30 min visual task followed by a 30 min rest. Based on our results, a 20 min rest for visual fatigue and VIMS recovery after a 15 min visual task on an OHMD and a 25 min rest for visual fatigue and VIMS recovery after a 30 min visual task on an OHMD are recommended. This study suggests a work-rest schedule for OHMDs that can be used as a reference for OHMD user guidelines to reduce visual fatigue and visually induced motion sickness.

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.

Baby carriers: a comparison of traditional sling and front-worn, rear-facing harness carriers.

The baby sling is a traditional baby carrier in Asia and the front-worn harness carriers are adapted in modern society. We compared the baby sling with front-worn harness carrier in terms of the physiological responses of the baby caregiver. Ten females (aged 23-32 years) and 10 males (aged 23-35 years) were recruited to participate in this study. Each subject was asked to carry two different weight baby dummies (7 and 10 kg) using three different baby carriers. The electromyography (EMG), shoulder tactile pressure, skin temperatures as well as heart rate were measured during baby carrying. The traditional baby sling and the two front-worn harness carriers showed little differences in EMG activities, shoulder tactile pressure and exercise intensity. Carrying two different weighted baby dummies caused significant differences in EMG and shoulder tactile pressure. Based on the findings of this study, recommendations about the improved baby carrier design are proposed. Practitioner Summary: This study compared traditional sling and front-worn harness baby carriers using caregivers' physiological responses including electromyography, shoulder tactile pressure, skin temperature and heart rate. Differences found between the carriers provide valuable information for baby carrier design and recommendations for the baby-carrying task.

Comparison of Barefoot Walking and Shod Walking Between Children with and Without Flat Feet.

BACKGROUND: We sought to investigate the effect of wearing shoes on joint range of motion, ground reaction force (GRF), and muscle activity (electromyography) in children with flat and normal feet during walking. METHODS: Nine children with flat feet and 12 children with normal feet aged 5 to 11 years were recruited. Each child was instructed to walk on a walkway in the barefoot and shod conditions. Joint range of motion, GRF, and electromyographic data within one gait cycle were collected simultaneously. Two-way analysis of variance was performed to evaluate the effects of foot type and shoe condition on the response measures. RESULTS: Children with flat feet had greater joint motion and higher muscle activities in the lower extremity, as well as lower vertical GRF and longer duration of the first peak forces in vertical and mediolateral GRFs than children with normal feet while walking. Compared with the barefoot condition, shoe wearing in both groups of children showed an increase in ankle dorsiflexion at heel strike, a decrease in anteroposterior GRF and its duration, and an increase in leg muscle electromyographic activities. Pelvic tilt range of motion was affected by the interaction of foot type and shoe condition. CONCLUSIONS: Gait performance in pelvic tilt, hip flexion, and ankle dorsiflexion were different between the two groups of children. Wearing shoes increased the muscle activities of the shin. This finding can provide important information for clinical assessment of and shoe design for children with flat feet.

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.

Taiwanese adult foot shape classification using 3D scanning data.

This study classifies the foot shapes of Taiwanese using 3D foot scanning data from 2000 males and 1000 females. Nine foot dimensions relative to foot length and absolute measures in the common foot length categories were applied to compare the gender differences. Using foot breadth in % foot length (% FL), ball of foot length in % FL and arch height in % FL as feature parameters, three foot shape types for males and females can be classified. Significant gender differences were found in seven of the nine foot dimensions. Females had greater ball of foot length than males (0.2% FL). When comparing feet of the same foot length, males had greater breadth, girth and height dimensions than females, except for toe height. In addition, ethnic differences in foot shape were also observed. The findings can provide very useful information for building gender-specific shoe lasts and designing footwear insoles. PRACTITIONER SUMMARY: 3D foot scanning data of 2000 males and 1000 females were classified into three different footshapes for males and females, respectively. Gender and ethnic differences on foot shape were also compared. The finding scan provide very useful information for gender-specific shoe last design and footwear production.

COMPARING 3D FOOT SHAPE MODELS BETWEEN TAIWANESE AND JAPANESE FEMALES.

This study compares foot shape and foot dimensions between Taiwanese and Japanese females. One hundred Taiwanese and 100 Japanese female 3D foot scanning data were used for comparison. To avoid the allometry effect, data from 23 Taiwanese and 19 Japanese with foot length between 233 to 237 mm were used for shape comparison. Homologous models created for the right feet of the 42 subjects were analyzed by Multidimensional Scaling. The results showed that there were significant differences in the forefoot shape between the two groups, and Taiwanese females had slightly wider feet with straighter big toe than Japanese females. The results of body and foot dimension comparison indicated that Taiwanese females were taller, heavier and had larger feet than Japanese females, while Japanese females had significantly larger toe 1 angle. Since some Taiwanese shoemakers adopt the Japanese shoe sizing system for making shoes, appropriateness of the shoe sizing system was also discussed. The present results provide very useful information for improving shoe last design and footwear fit for Taiwanese females.

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.

Interactions between task repetition and psychosocial factors.

Psychosocial factors, individual factors, workplace requirements, and workplace organizational factors have all been reported as being associated with the risk of musculoskeletal disorders [11]. Huang, Feuerstein, and Sauter [5] described the various concepts and models proposed to link occupational stress and work-related upper extremity disorders, as well as the difficulty in verifying the suggested linkages. Huang et al. [5] suggested that decomposing a complex model would be an appropriate method to begin the investigations of the proposed models. Task repetition is a workplace requirement that is considered a potential risk factor for cumulative trauma and its relationship to psychosocial factors was investigated. The study found only weak to no statistically significant relationship between task repetition and reported psychosocial factors of job stress in workers in Taiwan.

Gender and walking speed effects on plantar pressure distribution for adults aged 20-60 years.

This study investigates gender and walking speed (80%, 100%, 120% and 140% of preferred walking speed (PWS)) effects on plantar pressure parameters. In total, 30 healthy males and females, aged between 20 to 60 years, participated in this study. A plantar pressure measurement device was used to measure the peak pressure, peak force and contact area in six plantar zones. The results indicate that males had higher peak pressure and peak force in the medial toe and forefoot, as well as greater contact area in the central forefoot and heel areas. Females had greater contact area in the midfoot. Increased walking speed caused a significant increase in most of the response measures and the increase became more obvious when the speed was higher than 120% PWS. Although there was no significant interaction between gender and PWS, some gender differences were found. PRACTITIONER SUMMARY: Using percentage PWS provides a new perspective to discuss the effects of gender and walking speed on plantar pressure distribution. This study's findings can be very useful for footwear and orthotics design for different genders.

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 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.

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.

Flatfoot prevalence and foot dimensions of 5- to 13-year-old children in Taiwan.

BACKGROUND: The prevalence of flatfeet in normal and obese children has not been studied well in the past. The prevalence of flatfoot and foot dimensions of school children in Taiwan were investigated in this study. MATERIALS AND METHODS: One thousand twenty-four school children (549 boys and 475 girls) aged 5 to 13 years participated in this study. Fifteen foot dimensions were measured using a 3D coordinate measuring probe, digital tape measure and Harris mat imprint. Two-way ANOVA was conducted to evaluate the flatfoot and obesity effects on foot dimensions as well as on the change in foot size between weightbearing and nonweightbearing conditions. RESULTS: The prevalence of flatfoot for 5- to 13-year-old children was 28% with a decreasing trend with age. Boys had a significantly higher frequency for flatfoot than girls (chi-square = 26.3; p < 0.001). The prevalence of flatfoot was 35% in boys and 20% in girls. The percent of overweight and obese children was 20%. A significant difference in the prevalence of flatfoot occurred between normal-weight (27%), overweight (31%), and obese (56%) children (chi-square = 18.0; p < 0.001). The obesity effect was significant (p < 0.01) for most foot dimensions. However, the flatfoot effect was only significant (p < 0.05) on foot height for both genders. CONCLUSION: Obese children have a higher frequency of flatfoot, greater foot dimensions, and less change in foot width with weightbearing than normal weight children. Children with flatfeet have a lower foot height and greater foot length change than children with normal feet with weightbearing.

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.