The human factors of computer input using a mouse device

This thesis investigates how people select items from a computer display using the mouse input device. The term computer mouse refers to a class of input devices which share certain features, but these may have different characteristics which influence the ways in which people use the device. Although task completion time is one of the most commonly used performance measures for input device evaluation, there is no consensus as to its definition. Furthermore most mouse studies fail to provide adequate assurances regarding its correct measurement.Therefore precise and accurate timing software were developed which permitted the recording of movement data which by means of automated analysis yielded the device movements made. Input system gain, an important task parameter, has been poorly defined and misconceptualized in most previous studies. The issue of gain has been clarified and investigated within this thesis. Movement characteristics varied between users and within users, even for the same task conditions. The variables of target size, movement amplitude, and experience exerted significant effects on performance. Subjects consistently undershot the target area. This may be a consequence of the particular task demands. Although task completion times indicated that mouse performance had stabilized after 132 trials the movement traces, even of very experienced users, indicated that there was still considerable room for improvement in performance, as indicated by the proportion of poorly made movements. The mouse input device was suitable for older novice device users, but they took longer to complete the experimental trials. Given the diversity and inconsistency of device movements, even for the same task conditions, caution is urged when interpreting averaged grouped data. Performance was found to be sensitive to; task conditions, device implementations, and experience in ways which are problematic for the theoretical descriptions of device movement, and limit the generalizability of such findings within this thesis.

The impact of the introduction of visual display terminals on the job characteristics, job satisfaction and well-being of users in government offices

The proliferation of visual display terminals (VDTs) in offices is an international phenomenon. Numerous studies have investigated the health implications which can be categorised into visual problems, symptoms of musculo-skelctal discomfort, or psychosocial effects. The psychosocial effects are broader and there is mixed evidence in this area. The inconsistent results from the studies of VDT work so far undertaken may reflect several methodological shortcomings. In an attempt to overcome these deficiencies and to broaden the model of inter-relationships a model was developed to investigate their interactions and Ihc outputs of job satisfaction, stress and ill health. The study was a two-stage, long-term investigation with measures taken before the VDTs were introduced and the same measures taken 12 months after the 'go-live' date. The research was conducted in four offices of the Department of Social Security. The data were analysed for each individual site and in addition the total data were used in a path analysis model. Significant positive relationships were found at the pre-implementation stage between the musculo-skeletal discomfort, psychosomatic ailments, visual complaints and stress. Job satisfaction was negatively related to visual complaints and musculo-skeletal discomfort. Direct paths were found for age and job level with variety found in the job and age with job satisfaction and a negative relationship with the office environment. The only job characteristic which had a direct path to stress was 'dealing with others'. Similar inter-relationships were found in the post-implementation data. However, in addition attributes of the computer system, such as screen brightness and glare, were related positively with stress and negatively with job satisfaction. The comparison of the data at the two stages found that there had been no significant changes in the users' perceptions of their job characteristics and job satisfaction but there was a small and significant reduction in the stress measure.

Computer aided design and manufacture of form-rolls

Cold roll forming of thin-walled sections is a very useful process in the sheet metal industry. However, the conventional method for the design and manufacture of form-rolls, the special tooling used in the cold roll forming process, is a very time consuming and skill demanding exercise. This thesis describes the establishment of a stand-alone minicomputer based CAD/CAM system for assisting the design and manufacture of form-rolls. The work was undertaken in collaboration with a leading manufacturer of thin-walled sections. A package of computer programs have been developed to provide computer aids for every aspect of work in form-roll design and manufacture. The programs have been successfully implemented, as an integrated CAD/CAM software system, on the ICL PERQ minicomputer with graphics facilities. Thus, the developed CAD/CAM system is a single-user workstation, with software facilities to help the user to perform the conventional roll design activities including the design of the finished section, the flower pattern, and the form-rolls. A roll editor program can then be used to modify, if required, the computer generated roll profiles. As far as manufacturing is concerned, a special-purpose roll machining program and postprocessor can be used in conjunction to generate the NC control part-programs for the production of form-rolls by NC turning. Graphics facilities have been incorporated into the CAD/CAM software programs to display drawings interactively on the computer screen throughout all stages of execution of the CAD/CAM software. It has been found that computerisation can shorten the lead time in all activities dealing with the design and manufacture of form-rolls, and small or medium size manufacturing companies can gain benefits from the CAD/CM! technology by developing, according to its own specification, a tailor-made CAD/CAM software system on a low cost minicomputer.