Conventional Performance Index Research Articles

Quantification of regional myocardial dysfunction after acute ischemic injury.

Quantification of myocardial performance after regional ischemic injury is difficult because available performance indexes are markedly dependent on concurrent load changes. To develop a more load-insensitive index of myocardial function during ischemia, eight conscious dogs were instrumented to measure left ventricular pressure with micromanometers and myocardial segment length with ultrasonic dimension transducers. Preload was varied by transient vena caval occlusion during control conditions, after 15 min of coronary occlusion, and at intervals during 24 h of reperfusion. Acute ischemia shifted the linear relationship between segmental stroke work (SW) and end-diastolic segment length (EDL) rightward, diminishing the slope and increasing the chi-intercept. Preload recruitable work area (PRWA), defined as the area under the SW-EDL curve, reflected changes in both slope and intercept. During acute ischemia, conventional performance indexes and PRWA decreased significantly and required up to 24 h of reperfusion to return to control values. Of all parameters examined, PRWA was most responsive to prolonged ischemic dysfunction after reperfusion and was insensitive to concurrent load changes. Thus PRWA provides improved precision in quantifying of myocardial dysfunction after regional ischemic injury. This parameter should be especially useful in assessing the subtle effects of acute interventions designed to modify functional recovery.

Input spaces and output performance

The performance of an output is defined as the least upper bound of the absolute value of that output, as time ranges over the real numbers and the input ranges over an appropriate function space. The paper extends previous results by introducing useful input spaces. A simple relation is found between performance, the step response and a characteristic of the input space. Useful necessary and sufficient conditions for finite performance are derived. The new results are extended to multivariable systems. The appropriateness of various conventional performance indices is assessed by considering the appropriateness of their corresponding input spaces.

Assessment of eye dominance through response time.

The present study examined the effectiveness of a new technique for the assessment of eye dominance. 41 undergraduates of both sexes completed the Edinburgh Handedness Inventory, as well as two conventional performance indexes of eye dominance. Then each subject was positioned before the video monitor of a microcomputer and asked to view the monitor through a device that presented a different area of the monitor screen to each eye. In these two screen areas the digits 0 through 9 were randomly presented. Within every three trials the first two trials presented a digit to both eyes, and on the third trial a digit was presented to both eyes or to only one eye. There were 20 presentations of each kind: to both eyes, right eye, or left eye. The subject indicated whether the viewed digit was larger than or less than 4.5. This cognitive decision task was a constant in all trials. Analyses were performed on the third-trial response times, specifically, on the response time using right eye minus response time using left eye. For right-eyed people this was a positive number. As predicted, handedness, as assessed by the Edinburgh instrument, was significantly correlated with eyedness, as assessed by the response time procedure. The two conventional indexes of eyedness were also correlated with eyedness as assessed by the response time procedure. This procedure, then, provides a cardinal-scale measurement of degree of eye dominance.

Optimal Control With Chebyshev Minimax Performance Index

The optimal control of dynamical systems with conventional Mayer, Lagrange, and Bolza type performance indexes has been studied in some detail [1], [2], [3]. In the present paper, the optimal control of dynamical systems with a certain minimax type performance index, which cannot be expressed in the Mayer, Lagrange, or Bolza format, is studied. The form of the optimal control is described and certain geometric properties of the solution are discussed. Several examples are worked in detail to illustrate application of the proposed method of solution.