This study addresses an individual's performance, relating it to eyesight changes due to the aging of the individual and to color computer screens used for computer-based-instruction not designed specifically for older students. This study determines how existing research in gerontology, human-computer interface, and color use in visual graphics can be applied to the design of computer screen displays containing color text and backgrounds and how various color combinations will affect performance by adult learners forty years of age and older. The results of this research provide software developers and instructional designers guidelines to use when designing computer screen displays for use in instructional computing settings involving older adults.

Electronic surveillance of employee performance is a common practice in the workplace today. Despite the fact that electronic monitoring is an inexpensive and objective technique for recording productivity figures, much resistance to the technique exists. The current study was conducted to determine if user acceptability and productivity could be improved in performance monitoring systems. It was hypothesized that frequent performance feedback would enhance productivity and task satisfaction as long as the feedback was not too frequent and the performance standard was not too difficult. The results of this experimental investigation did not support this hypothesis indicating that productivity (in terms of the amount of data entered into computer files) was actually higher when the performance standard was difficult and the performance feedback frequent. In addition, subjects assigned to the Difficult Goal/Frequent Feedback condition were more satisfied with the task and performance feedback than other subjects. Results are discussed in light of current viewpoints in applied psychology and human-computer interaction. / Ph. D.

Five commercially available touch entry devices (TEDs) were the  subject of a four-phase comprehensive assessment. Phase I consisted of the quantification of CRT-TED optical quality involving photometric measurements. Phase II involved the measurement and analysis of interactive operator performance in three generic tasks. Phase II was followed by the recording of subjective assessments of TED utility (Phase III). In Phase IV correlational analyses were conducted to relate CRT-TED system optical quality to the interactive performance measures and subjective assessments of TED utility collected in Experiment 1 of Phases II and III. A methodology for determining display quality of CRTTED systems in a quantitative manner as well as the operational and subjective utility of TEDs is presented. The results point out that large difference in resolution and noise levels exist among the various TEDs examined. Four of the devices tended to reduce overall display resolution and three reduced display noise levels. Large differences in interactive operator performance scores and ratings of subjective utility exist as well. There is some relationship between CRT-TED optical quality and both operator performance and subjective assessments of TED utility. Moreover, the suggested quantifications of the findings should facilitate comparisons among other touch entry device systems. / M.S.

This dissertation examined the effects of display spatial luminance nonuniformities on operator performance and perception. The objectives of this research were to develop definitions of nonuniformity, develop accurate measurement techniques, determine acceptable levels of nonuniformities, and to develop a predictive model based on user performance data. Nonuniformities were described in terms of spatial frequency, amplitude, display luminance, gradient shape, and number of dimensions. Performance measures included a visual random search task and a subjective measure to determine users' perceptions of the nonuniformities. Results showed that users were able to perform the search task in the presence of appreciable nonuniformities. lt was concluded that current published recommendations for acceptable levels of nonuniformities are adequately specified. Results from the subjective task showed that users were sensitive to the presence of nonuniformities in terms of their perceptions of uniformity. Specifically, results showed that as spatial frequency increased, perceived uniformity ratings increased. That is, users rated nonuniformities to be less noticeable. As amplitude and display luminance increased, the users' ratings of perceived uniformity decreased; that is, they rated the display as being farther from a uniform field. There were no differences in impressions between a sine and triangle gradient shape, while a square gradient shape resulted in lower ratings of perceived uniformity. Few differences were attributed to the dimension (1-D versus 2- D) of the nonuniformity and results were inconclusive because dimension was confounded with the display luminance. Nonuniformities were analyzed using Fourier techniques to determine the amplitudes of the coefficients for each nonuniformity pattern. These physical descriptors were used to develop models to predict users' perceptions of the nonuniformities. A few models yielded good fits of the subjective data. lt was concluded that the method for describing and measuring nonuniformities was successful. Also, the results of this research were in strong concurrence with previous research in the area of spatial vision. / Ph. D.

This dissertation was a two-phase effort. Phase I investigated the physical image quality of 16 mesh, etched, and quarterwave antireflection filters for varying levels of filter transmissivity. Three levels of ambient lighting and two levels of monochrome CRT resolution were combined factorially with the filters. In addition, user measures of readability, legibility, and perceived image quality were obtained for these same filter and environmental conditions. Quantitative models were developed to predict the performance and subjective data based on signal and noise measures derived from the physical measurements. Phase II examined the effects of a wide range of filter transmissions and diffuse illuminance on measured image quality and the same user measures as in Phase I. Phase I showed that while none of the glare filters yielded improved readability or legibility over a baseline condition, the etched and low transmission filters were notable for their degradation of human performance. Mesh and quarterwave filters were found to improve perceived image quality when a specular glare source was present. Modeling was minimally successful for the reading and legibility tasks, but yielded good fit models for perceived image quality. Phase II showed that when even extreme losses in display contrast occurred, users were capable of good reading and legibility performance. Perceived image quality was inversely related to illuminance level. Prediction of performance by image quality metrics was generally not too successful. It was concluded that in office-type environments, mesh or quarterwave filters can be used to improve perceived image quality when specular glare sources are present, but that no anti-glare filters yielded enhanced short-term readability or legibility over a baseline. Etched filters were not recommended. Measures of physical image quality proved to be good predictors of perceived image quality, but not of timed measures of readability or legibility. Under moderate lighting conditions, monochrome CRTs should be fitted with fairly high transmission filters as it was found the contrast enhancement offered by low transmission filters had negligible effects on performance. Finally, consistent and repeatable findings of degraded legibility for high luminance contrast levels (low illuminance) generated questions as to the existing standards regarding maximum contrast requirements for CRT use. / Ph. D.

Work related musculoskeletal disorders (WMSD) remain the focus of research efforts as costs associated with these disorders range from 13 to 54 billion dollars annually. WMSDs associated with the back and neck compromise almost 27% of all reported WMSDs. Approximately 1/3 of visual display terminal (VDT) operators report back and neck pain annually (BLS, 1998). Physical risk factors of VDTs associated with low back and neck WMSDs include static work postures and workstation design. The objectives of this study were to assess the effects of monitor height, chair type and their interaction on task performance, back/neck electromyography (EMG), perceived discomfort, and number of posture shifts. Both monitor height and chair type were assessed using two levels (high and low). Participants, four male and four female college age students, performed two data entry tasks using a standard keyboard and monitor and a fully adjustable bi-level table. In addition to the experimenter defined workstation configurations, participants were allowed to adjust their workstation to their preferred settings. Analysis of variance was performed to assess differences in task performance, perceived level of discomfort, number of posture shifts, and EMG data associated with various combinations of monitor height and chair type. Correlation analysis was performed to assess the relationship between participant's perceived discomfort and measured muscle activity to help determine if these two measurements could be used interchangeably to assess workstation design. No effect of workstation configuration (monitor height/chair type) was found for the majority of dependent variables. An exception was that configuration of low monitor, high chair, and their interaction generated significantly more muscle activity for the low back. User preferred settings were not found to differ significantly from those investigated with respect to muscle activity, perceived discomfort, posture shifts, and performance. Additionally, it was found the participants chose to position the iii workstation according to guidelines suggested in the literature for reducing WMSD discomfort. Task effects were found for performance, posture shifts, and perceived level of discomfort. Higher levels of performance and posture shifts for the neck were associated with the typing task, as opposed to the math task. Higher levels of neck discomfort, posture shifts of the feet and posture shifts of the back were associated with the math task. Correlation analysis provided evidence that perceived discomfort reported by participants and muscle activity for job tasks may not be related. Observed muscle activity for the tasks investigated in this study was low and in some instances, close to resting activity. Due to low levels of EMG, participants may not have been cognizant of their back and neck muscle activity, offering an explanation for why participants experience a cumulative effect of workstation design and seated postures, but linking particular causal factors to the development of LBP and NP is difficult. The findings of this study suggest that there are no gross physical differences between the chair types or monitor heights as defined in this study. Other factors (such as user preferences, job task demands, specific chair parameters, etc.) may significantly effect chair selection. This study found that task was a significant effect for the majority of dependent variables, and therefore may need to be a major factor driving workstation design. Workstation configuration will help determine the type of static posture assumed at a workstation, but the "discomfort or number of posture shifts" associated with that workstation and posture might be more a result of the job task requirements. / Master of Science

Much concern has been expressed about the ability of the visual display terminal to provide adequate stimuli for accommodation. As a result it has been hypothesized that an observer may have to continually refocus to maintain accommodation on the display and this contributes to the visual fatigue experienced by VDT users. The increased use of multicolor CRTs in the workplace adds yet another factor, chromatic aberration, to affect the observers' accommodation to information presented on the CRT. Two experiments were run to determine the effect of viewing characters of one chromaticity and purity on a background of another chromaticity or purity or chromaticity and purity. The observer's accommodation response was continuously sampled throughout the presentation of each target/background combination. Mean accommodation response and the standard deviation of the mean accommodation response were then calculated to ascertain the effect the target background combination had on the observers' accommodation response. The observers' were also required to perform a visual performance task for each target/background combination. The data collected indicate that chromatic characters when observed on chromatic background do not provide a strong stimulus for accommodation. Mean changes in the observers accommodation response were all within the depth of field except when characters were viewed on blue backgrounds. The variability in the observers accommodation response was not found to be a good predictor of image quality where only color contrast exists between foreground and surround. Task performance was highly correlated with effective contrast between the target and background as quantified by uniform color space modeling. / Ph. D.

The effects of manipulating two parameters of legibility; matrix/character size and font, on two performance measures, reading times and eye movements, were studied in this experiment. The results showed significant practice effects for the 7 x 9, 7 x 9 (= 5 x 7), and 9 x 11 (= 5 x 7) sizes. The data also showed that the size of a character had some effect on both the duration of fixations and the duration of saccades. There was little or no correlation among the response measures of eye movements, tachistoscopic recognition, and reading times. / M. S.

This study is concerned with determining the effects that video display terminal use had on reporters' and editors' attitudes toward their jobs and the machines themselves. Data for this investigation were obtained with questionnaires returned from seventy-one reporters and editors who use video terminals in their daily work. Questionnaire data were supplemented with interview data from thirteen questionnaire respondents, Ten hypotheses in five categories were tested with the t test. Four additional hypotheses were tested with raw data. Findings showed that video terminal use enhanced perceived job professionalism and made respondents think they should make more money. Attitudes toward video terminals improved after use of the devices, and respondents recognized the value of video terminal training in college,

Small Unmanned Aerial Vehicles (SUAVs) are an attractive choice for many surveillance tasks. However, video from an SUAV can be difficult to use in its raw form. In addition, the limitations inherent in the SUAV platform inhibit the distribution of video to remote users. To solve the problems with using SUAV video, we propose a system to automatically create geo-referenced mosiacs of video frames. We also present three novel techniques we have developed to improve ortho-rectification and geo-location accuracy of the mosaics. The most successful of these techniques is able to reduce geo-location error by a factor of 15 with minimal computational overhead. The proposed system overcomes communications limitations by transmitting the mosaics to a central server where there they can easily be accessed by remote users via the Internet. Using flight test results, we show that the proposed mosaicking system achieves real-time performance and produces high-quality and accurately geo-referenced imagery.