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This study evaluated the potential effectiveness of screen filters in relieving visual fatigue. Critical flicker frequency (CFF), accommodation power, visual acuity, and subjective rating of visual fatigue were evaluated at four different stages: without screen filter, screen filter use of 2.5 mo., 5 mo., and 12 mo. For each stage, all measurements were taken before and after an 8-hr. workday. Analysis of variance was performed to test whether the screen filter use or measurement time had a significant effect on any of the visual fatigue measurements. The results indicated visual acuity was significantly improved after the use of a screen filter, while after the screen filter was installed, the CFF reading showed visual fatigue was more pronounced. Significant improvement in subjective ratings of double vision on screen was found after the screen filter use of 2.5 mo., but improvements disappeared after continuous use at 5 too. A Hawthorne effect could have contributed to the short-term relief in visual fatigue and inconsistent findings in other visual performance measurements. Sorting out frequently used questions into a few definable areas and data sets might reduce the screen viewing time and visual fatigue more effectively.

The study derived seven descriptors from the pixel matrices of both the uppercase and lowercase forms of the 26 letters in the English alphabet in the regular and italic versions of the most commonly used font, Times New Roman. A factor analysis of the seven descriptors showed that a two-factor solution of letter width and height explained 76.6% of the variance. Legibility threshold of the 26 letters in the regular and italic Times Roman font and in two-case forms were collected to specify effects of letter width and height. 20 university students, 10 women and 10 men, with a mean age of 24.1 yr. (SD = 1.6) participated. They identified letters displayed initially on a PC screen at a minimum font size and enlarged gradually until the participant correctly recognized the letter. Analysis showed letters of greater width or height were more legible than those of smaller width or height. Given an oblique effect, letters in the italic Times Roman font had significantly greater width but were less legible than those in the regular font.

Potential ergonomic hazards for 27 disabled call center agents engaged in computer-telephone interactive tasks were evaluated for possible associations between the task behaviors and work-related disorders. Data included task description, 300 samples of performance, a questionnaire on workstation design, body-part discomfort rating, perceived stress, potential job stressors, and direct measurement of environmental factors. Analysis indicated agents were frequently exposed to prolonged static sitting and repetitive movements, together with unsupported back and flexed neck, causing musculoskeletal discomforts. Visual fatigue (85.2% of agents), discomfort of ears (66.7%), and musculoskeletal discomforts (59.3%) were the most pronounced and prevalent complaints after prolonged working. 17 of 27 agents described job pressure as high or very high, and dealing with difficult customers and trying to fulfill the customers' needs within the time standard were main stressors. Further work on surrounding noise, earphone use, possible hearing loss of experienced agents, training programs, feasible solutions for visual fatigue, musculoskeletal symptoms, and psychosocial stress should be conducted.

Contributing factors to 621 occupational fatal falls have been identified with respect to the victim's individual factors, the fall site, company size, and cause of fall. Individual factors included age, gender, experience, and the use of personal protective equipment (PPE). Accident scenarios were derived from accident reports. Significant linkages were found between causes for the falls and accident events. Falls from scaffold staging were associated with a lack of complying scaffolds and bodily action. Falls through existing floor openings were associated with unguarded openings, inappropriate protections, or the removal of protections. Falls from building girders or other structural steel were associated with bodily actions and improper use of PPE. Falls from roof edges were associated with bodily actions and being pulled down by a hoist, object or tool. Falls through roof surfaces were associated with lack of complying scaffolds. Falls from ladders were associated with overexertion and unusual control and the use of unsafe ladders and tools. Falls down stairs or steps were associated with unguarded openings. Falls while jumping to a lower floor and falls through existing roof openings were associated with poor work practices. Primary and secondary prevention measures can be used to prevent falls or to mitigate the consequences of falls and are suggested for each type of accident. Primary prevention measures would include fixed barriers, such as handrails, guardrails, surface opening protections (hole coverings), crawling boards/planks, and strong roofing materials. Secondary protection measures would include travel restraint systems (safety belt), fall arrest systems (safety harness), and fall containment systems (safety nets). Keywords: Fatal falls; Falls from height; Construction ergonomics; Construction site safety

The current experiment tested the aiming accuracy of the eye for targets at nine different positions and of two different sizes. The left eye was tracked to record the line of gaze with an infrared eye-monitoring device. For each subject, horizontal shift, vertical shift, standard deviations of the X and Y coordinates, and 95th percentile of the horizontal and vertical shifts from the nine target centers were calculated to indicate the precision, accuracy, and possible design limits of the gaze points. Analysis showed that the target's position had a strong effect on the vertical shift, standard deviations of the Y coordinate, and 95th percentile of the vertical shift. The effect of target size was not significant on any of the dependent measures. The research findings have important implications for the redesign of the gaze-pointing device. Visual targets appearing below the horizontal line of sight should be larger than those above. based on the 95th percentile of the horizontal and vertical shifts, targets should be approximately 2.0 [degrees] wide and 2.4 [degrees] long above or coinciding with the horizontal line of gaze and 2.6 [degrees] wide and 3.9 [degrees] (cm) long below the horizontal line of gaze.

The current experiment examined the speed-accuracy trade-off of saccadic movement between two targets. Ten subjects looked alternately at two targets as fast and as accurately as possible for 2 min. under different conditions of target size, distance between targets, and direction of eye movement. Saccadic movement of the left eye was tracked and recorded with an infrared eye monitoring device to compute the starting position, ending position, and duration of each saccadic movement. Eye-movement time was significantly related to target size and distance between targets, but the speed-accuracy trade-off was significantly different from that predicted by Fitts' Law. Reaction time was not significantly changed by the direction of eye movement.

This research investigated human visual sensitivity and bias in inspecting irregular objects. A preliminary study was conducted using the method of constants to determine the threshold value for judgment of size. A factorial experiment was conducted using payoffs, rate of defective items, and detectability in the signal-detection theory as the factors. In total, eight experimental conditions were tested. 10 college students were recruited as subjects. Each subject was asked to compare 40 teapot shapes to a standard teapot shape under eight experimental conditions. Defective shapes were generated by lengthening the vertical dimension of a standard teapot shape by a factor of 1.01 and 1.04 for 'low' and 'high' detectability. The decision time and responses of 'identical' or 'different' were collected under all experimental conditions. Analysis indicates that the decision-making strategy used to inspect this irregular object was very close to maximizing the accuracy of decision-making by considering the rate of defective items. This result is different from most research findings in signal-detection theory in which responses of human beings are similar to degraded Bayes optimizers. The standard deviation of the signal distribution was about 1.30 and 1.41 times that of the noise distributions for 'low' and 'high' detectability.

The purpose of this research was to develop a new model to describe and predict a computerized task. AutoCAD was utilized as the experimental tool to collect operating procedure and time data at a keystroke level for a computer aided design (CAD) task. Six undergraduate students participated in the experiment. They were required to complete one simple and one complex engineering drawing. A model which characterized the task performance by software commands and predicted task execution time using keystroke-level model operators was proposed and applied to the analysis of the dialogue data. This task parameter model adopted software commands, e.g. LINE, OFFSET in AutoCAD, to describe the function of a task unit and used up to five parameters to indicate the number of keystrokes, chosen function for a command, and ways of starting and ending a command. Each task unit in the task parameter model can be replaced by a number of primitive operators as in the keystroke level model to predict the task execution time. The observed task execution times of all task units were found to be highly correlated with the task execution times predicted by the keystroke level model. Therefore, the task parameter model was proved to be a usable analytical tool for evaluating the human-computer interface (HCI). Keywords: task analysis, GOMS model, computer-aided design (CAD)

Optimization models of human visual search performance can be constructed that assume that the human operator maximizes an objective function, subject to given constraints. Two experiments were performed to validate [...]

The bikeshare program in Taipei City and New Taipei City, called U-bike, was launched in August 2012 and has more than 7500 bicycles operating out of 769 stations. Research has suggested that bicycle helmet use is a means of reducing morbidity and mortality among bike users. Helmets, however, are not available for rent when a U-bike is rented. The current research conducted an observational study to examine the prevalence of helmet non-use by users of the bikeshare program, electric bicycles, racing bicycles, and personal bicycles in Taipei City and New Taipei City. Trained observers using compact video cameras collected helmet non-use data during various times of the day and on different days of the week. Observers collected data on cyclist attributes, bicycle types, and helmet use at several selected locations within Taipei City and New Taipei City. U-bike users were found to be the least likely to wear helmets. Other noteworthy findings include that violations such as phone use, red-light violations, and travelling at ≥25 km/h were associated with riding without a helmet. Male users of racing bikes tended not to wear helmets, while female users of other bicycle types were less likely to use a helmet. Carrying passengers by users of electric bikes and personal bikes was a determinant of helmet non-use. This paper concludes with a discussion and recommendations for future research. [ABSTRACT FROM AUTHOR]

The current study investigated occupational risk of handicapped workers relative to nonhandicapped workers and used the standardized mortality ratio as an index that handicapped workers were at elevated risk for occupational injury. A total of 6,327 records of disabling occupational injuries beyond first aid treatment from January to December, 1999 were collected and analyzed. The ratio of the standardized mortality ratio of the handicapped vs nonhandicapped workers indicated that occupational injury risk of handicapped workers must be seriously examined for the reasons for this unexpectedly high occupational risk.

The current study measured the critical elements of jobs and characterized the jobs' suitability for aging workers based on ratings of those elements. The sample consisted of 830 job titles collected by the Employment and Vocational Training Administration in Taiwan. For each job the ratings of 45 specific variables, falling into three major classes, were factor analyzed, using principal components analysis with varimax rotation. A nine-factor solution explained 50.1% of the variance. Using a nonhierarchical clustering procedure, 830 jobs were classified into three homogeneous clusters which were significantly different on nine factors except for Manual Dexterity. Mapping the ratings on the 9 factors and the characteristics of aging workers, the four job clusters were defined as Age-enhanced, Age-neutral, and Age-counteracted, and Age-impaired to describe the suitability for aging workers.

INTRODUCTION Visual display terminals (VDTs) can be used to store and convey static and dynamic visual information, and thus they have inevitably become interfaces in both the office and the […], We compared 7 methods of measuring visual fatigue - accommodation power, visual acuity, pupil diameter, critical fusion frequency (CFF), eye movement velocity, subjective rating of visual fatigue, and task performance - for their sensitivity to visual load. In the experiment, 10 participants performed a monitoring task at 2 viewing distances, read articles under 2 levels of screen contrast, and tracked visual targets at 2 different speeds. The same measurement techniques, excluding pupil diameter and eye movement velocity, were compared by extending the task time from 20 to 60 min with the same VDT tasks to test for possible improvement in sensitivity. The results indicated that sensitivities of accommodation power, visual acuity, and CFF were greatly improved by a longer task period, but these 3 measurement techniques did not distinguish among tasks. Pupil diameter, eye movement velocity, and subjective rating of visual fatigue were sensitive in differentiating tracking from reading and monitoring tasks. Eye movement velocity and subjective rating were sensitive to the changes in target velocity of the tracking task. Although task performance was not directly comparable to other measurement techniques, it helped to ensure that participants maintained the same performance level by devoting more resources to the high-load conditions. Actual or potential applications of this research include using some of these assessment techniques for the design of adaptive displays.

Many disabled individuals lack extensive knowledge about assistive technology, which could help them use computers. In 1997, Denis Anson developed a decision tree of 49 evaluative questions designed to evaluate the functional capabilities of the disabled user and choose an appropriate combination of assistive devices, from a selection of 26, that enable the individual to use a computer. In general, occupational therapists guide the disabled users through this process. They often have to go over repetitive questions in order to find an appropriate device. A disabled user may require an alphanumeric entry device, a pointing device, an output device, a performance enhancement device, or some combination of these. Therefore, the current research eliminates redundant questions and divides Anson's decision tree into multiple independent subtrees to meet the actual demand of computer users with disabilities. The modified decision tree was tested by six disabled users to prove it can determine a complete set of assistive devices with a smaller number of evaluative questions. The means to insert new categories of computer-related assistive devices was included to ensure the decision tree can be expanded and updated. The current decision tree can help the disabled users and assistive technology practitioners to find appropriate computer-related assistive devices that meet with clients' individual needs in an efficient manner. [ABSTRACT FROM PUBLISHER]

A dynamic visual information processing task was designed to investigate time-based and intensity-based factors on an operator's information processing load as measured by reaction time, pupil diameter, and eye movement parameters. The time-based factor was manipulated by the target rate and scanning rate while the intensity-based factor was manipulated by the difference between a simple reaction task and a physical matching (choice reaction) task. Nine participants tracked the scanning line at two different scanning rates and were required to respond to two designated targets presented singly at two different temporal frequencies. The results indicated that task difficulty (the intensity-based factor) had a significant effect on the reaction time. Target rate and scanning rate were integrated as one time-based factor in terms of three sweeping angles. The time-based factor was found to have a significant effect on the fixation time, saccade amplitude, fixation frequency, eye movement speed, reaction time and hit rate. No interaction effect was found between time-based and intensity-based factors. The time pressure (defined by the time required divided by the time available) based on a model human processor was positively related to scanning rate, target rate and task difficulty. It was found to be the most objective and reliable if time required can be reliably predicted based on a predictive model approach. [ABSTRACT FROM AUTHOR]

As inspection moves from unaided human skills to human-computer hybrid tasks, there is a need for models of the human and the computer which have common parameters. With appropriate models, functions can be allocated to produce optimal designs, and assistance provided to the human inspector via job aids and training. A model was developed of the human in a two-component compound inspection task consisting of search and decision. Optimizing this model showed that the choice of optimal values of parameters in the two submodels was independent. Ten subjects were tested on a two-component inspection task, using components which had earlier been validated separately. Subjects showed some aspects of optimum behaviour, for example sub-model independence, stopping the search after an integral number of scans, and varying their decision criteria to respond to the probability and cost structure. However, in this more complex task, subjects often reverted to simpler decision rules, for example always stopping the search after one scan or accepting (or rejecting) all potential defects detected. The implication for hybrid automation systems is that humans will need help such as job aids or training if they are to perform optimally when given both search and decision tasks. [ABSTRACT FROM AUTHOR]