Total Task Completion Research Articles

Objective measurement and subjective rating of system performance in remote manipulation

In the present experiment we investigate the usefulness of stereoscopic TV displays for performing remote manipulation tasks. We required a group of relatively inexperienced manipulator operators to perform a complex and difficult remote line threading task and varied the visual di splay combinations available to the operators while performing this task. For each video display condition tested, the operator sat in a centered position facing two CRT’s, each providing a separate view of the remote task site. Total task completion times, manipulative errors, operator gaze preferences, and subjective ratings of lask difficulty were measured for each combination of display types. Results show a strong and consistent operator viewing preference for stereoscopic displays as well as substantial and statistically significant performance advantages for those display combinations that included a stereoscopic view.

Optimal design and use of retry in fault-tolerant computer systems

In this paper, a new method is presented for (i) determining an optimal retry policy and (ii) using retry for fault characterization , which is defined as classification of the fault type and determination of fault durations. First, an optimal retry policy is derived for a given fault characteristic, which determines the maximum allowable retry durations so as to minimize the total task completion time. Then, the combined fault characterization and retry decision, in which the characteristic of a fault is estimated simultaneously with the determination of the optimal retry policy, are carried out. Two solution approaches are developed: one is based on point estimation and the other on Bayes sequential decision analysis. Numerical examples are presented in which all the durations associated with faults (i.e., active, benign, and interfailure durations) have monotone hazard rate functions (e.g., exponential Weibull and gamma distributions). These are standard distributions commonly used for modeling and analyses of faults.