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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]