An improved Web search engine for visually impaired users

The Google search engine was studied as a Web prototype to be modified and improved for blind users. A Specialized Search Engine for the Blind (SSEB) was developed with an accessible interface and improved functions (searching assistance functions, user-centered functions, and specialized design for the blind). An experiment was conducted with twelve participants, both blind and sighted, to verify the effects of SSEB. The performance was better with the SSEB than with the Google search engine, and the participants also showed higher satisfactions with the SSEB. Interface considerations for designing an accessible Web site for blind users are important. The users of SSEB could in the future be expanded to include most, if not all, visually impaired people, since the World Wide Web and all Internet resources should ideally be accessible to everyone.     

An optimal range of information quantity on computer-based procedure interface design in the advanced main control room

The quantification of information in the interface design is a critical issue. Too much information on an interface can confuse a user while executing a task, and too little information may result in poor user performance. This study focused on the quantification of visible information on computer-based procedures (CBPs). Levels of information quantity and task complexity were considered in this experiment. Simulated CBPs were developed to consist of three levels: high (at least 10 events, i.e. 3.32 bits), medium (4–8 events, i.e. 2–3 bits), and low information quantity (1 or 2 events, i.e. 0 or 1 bits). Task complexity comprised two levels: complex tasks and simple tasks. The dependent variables include operation time, secondary task performance, and mental workload. Results suggested that medium information quantity of five to eight events has a remarkable advantage in supporting operator performance under both simple and complex tasks. This research not only suggested the appropriate range of information quantity on the CBP interface, but also complemented certain deficient results of previous CBP interface design studies. Additionally, based on results obtained by this study, the quantification of information on the CBP interface should be considered to ensure safe operation of nuclear power plants.     

Experimental studies of computerized procedures and team size in nuclear power plant operations

The operation of a nuclear power plant is so complex that it requires teamwork. To support team performance, a system need to provide all team members integrated information displays as well as decision aids (e.g., computerized procedures). Two experiments were conducted to investigate the effects of computerized procedures and team size on operating performance. Forty-five participants were involved in the experiments. Each participant executed decision and action tasks to deal with alarm signals, while detecting occasional system errors in the interface. Results showed that effects of computerized procedures were significant on various performance indicators, such as operation time, operation errors, and learning effect, and that two operators would be a satisfactory size in the teamwork system providing computerized procedures.     

The development of mental workload measurement in flexible manufacturing systems

The purpose of this study is to determine an appropriate index to measure the mental workload in supervisory tasks. Nine elements relevant to the supervisory task were formed into a “Test Bank” after the task was analyzed. The reliability and validity of the “Test Bank” were examined. Then an experiment with simulated FMS was conducted to acquire the multiple regression equation of certain elements. The results reveal that “span,” “discriminate,” “predict,” and “transfer attention” are important elements. We can use the equation to predict the mental workload of a human operator in an automated production system. © 1998 John Wiley & Sons, Inc.     

A stochastic model of human errors on system reliability

An analysis of system reliability is presented in this study by taking into account latent human error and recovery factors. The purpose is to estimate system reliability more accurately. Stochastic process methods are applied to generate system reliability models. Three different models, each representing specific recovery types, have been developed. The results show that system reliability varies depending on the type of recovery, and may provide system designer with suggestions as to how to improve system reliability.     

A performance measuring model for dynamic quality characteristics of human decision-making in automation

Automation system operating performance (ASOP) is a concept of how well an automation unit (AU) is monitored and performed by supervisors. The purpose of this paper was to study the ASOP for dynamic characteristics of human decision-making in automation. First, a quantitative ASOP measuring model was proposed. Secondly, a matrix and orthogonal experiment was conducted to verify the model, specifically on ASOP measuring. The experimental results indicated that the quality-objective function (eta) of human dynamic decision-making characteristics to measure the ASOP is easy and objective, and, according to the eta value, one can obtain the optimal ASOP by the best combination of levels of the control factors. The results of this study indicates that the quality-objective function can be regarded as measuring standard of ASOP and evaluating standard of selecting the adapted supervisors in automation, and some inferences from experimental results can be applied to the design of human-machine interface.     

The effects of platform motion and target orientation on the performance of trackball manipulation

The trackball has been widely employed as a control/command input device on moving vehicles, but few studies have explored the effects of platform motion on its manipulation. Fewer still have considered this issue in designing the user interface and the arrangement of console location and orientation simultaneously. This work describes an experiment carried out to investigate the performance of trackball users on a simple point-and-click task in a motion simulator. By varying the orientation of onscreen targets, the effect of cursor movement direction on performance is investigated. The results indicate that the platform motion and target orientation both significantly affect the time required to point and click, but not the accuracy of target selection. The movement times were considerably longer under rolling and pitching motions and for targets located along the diagonal axes of the interface. Subjective evaluations carried out by the participants agree with these objective results. These findings could be used to optimise console and graphical menu design for use on maritime vessels. STATEMENT OF RELEVANCE: In military situations, matters of life or death may be decided in milliseconds. Any delay or error in classification and identification will thus affect the safety of the ship and its crew. This study demonstrates that performance of manipulating a trackball is affected by the platform motion and target orientation. The results of the present study can guide the arrangement of consoles and the design of trackball-based graphical user interfaces on maritime vessels.     

The effects of in-vehicle tasks and time-gap selection while reclaiming control from adaptive cruise control (ACC) with bus simulator

This research aimed to find out the effects of in-vehicle distractions and time-gap settings with a fix-based bus driving simulator in a following scenario. Professional bus drivers were recruited to perform in-vehicle tasks while driving with adaptive cruise control (ACC) of changeable time-gap settings in freeway traffic. Thirty subjects were divided equally into three groups for different in-vehicle task modes (between subjects), including no task distraction, hands-free, and manual modes. Further, time-gap settings for the experimental ACC were: shorter than 1.0 s, 1.0–1.5 s, 1.5–2.0 s, and longer than 2.0 s (within subjects). Longitudinal (mean headway, forward collision rate, and response time) and lateral control (mean lateral lane position and its standard deviation) performance was assessed. In the results, longitudinal control performance was worsened by both shorter time-gaps and heavier in-vehicle tasks. But the interaction indicated that the harm by heavier in-vehicle distraction could be improved by longer time-gaps. As for the lateral control, it would only be negatively affected by shorter time-gap settings. This research indicates the effects of time-gaps and in-vehicle distraction, as well as the interaction. Proper time-gap selection under different in-vehicle distractions can help avoid accidents and keep safe.     

Optimization of Chinese interface design in motion environments

The Taguchi method has been successfully applied in engineering fields to deal with a single performance quality problem, but it is not often used in interface design and the handling of multiple performance quality problems. This study investigated a multi-response problem in terms of searching time, number of missing characters/buttons (NMCB), and visual fatigue by integrating the Taguchi method and the weighting method to optimize the Chinese interface design parameters such as display type, character size, font type, and text/background color combination in motion environments. The results indicated that subjects’ visual performance was improved when using the optimum interface setting (LCD, 7.5 * 7.5 mm, Kai font and white/blue color combination) rather than the current interface setting.     

Application control chart concepts of designing a pre-alarm system in the nuclear power plant control room

This study applied the concepts of the Shewhart control chart to design a pre-alarm system for the nuclear power plant control room. As a support in detecting faults, the pre-alarm system reminded the operators of a change in the system state in its early stages. Two pre-alarm types were designed to compare with the original system, and all participants were requested to monitor each simulated system under both normal and abnormal states. The tasks for the participants included shutting down the reactor, searching for procedures, monitoring system parameters and executing secondary tasks. In each trial, the task performance, mental workload and situation awareness (SA) of the participants were measured. Results indicated that participants had lower mental workload, but equal SA, when monitoring the system with either type of pre-alarm designs, and lower alarm frequency and higher secondary task performance were obtained with the pre-alarm design. Therefore, the pre-alarm system effectively assisted the operators in monitoring tasks.