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At least 775 records · Page 43Linked to original sources
PubMed1987

On the use of the cause table in handling common cause events in system analysis.

A method is presented for applying the cause table concept to the problem of common cause events. This method can be regarded as an alternative to the approach in which these events are included directly into the system fault trees. In comparison with this approach, the cause table method offers the advantage of simple fault trees, convenient visibility of the contributions of causes, and the ability to truncate the numerical calculation conveniently by aggregating small terms into an "other" category. Generally speaking, the cause table method can be said to handle common causes at the level of arithmetic (i.e., numbers) rather than at the level of algebra (determining cutsets and frequency equations).

Methods↗
PubMed1996

On the existence of a lactate threshold during incremental exercise: a systems analysis.

The relationship between blood lactate concentration ([La]) and O2 uptake (VO2) during incremental exercise remains controversial: does [La] increase smoothly as a function of VO2 (continuous model), or does it begin to increase abruptly above a particular metabolic rate (threshold model)? The dynamic characteristics of the underlying physiological system are investigated using system identification analysis techniques. A multivariate deterministic time series model of the [La] and VO2 response to incremental changes in work rate was fitted to simulated and experimental data. Time-varying system response parameters were determined through the application of a weighted recursive least squares algorithm. The model, using the identified time-varying parameters, provided a good fit to the data. The variation of these parameters over time was then examined. Two major transitions in the parameters were found to occur at intensity levels equivalent to 53 +/- 8% and 77 +/- 9% maximal VO2 (experimental data). These changes in the model parameters indicate that the best linear dynamic model that fits the observed system behavior has changed. This implies that the system has changed its operation in some way, by altering its structure or by moving to a different operating region. The identified parameter changes over time suggest that the exercise intensity range (from rest to maximal VO2) is divided into three main intensity domains, each with distinct dynamics. Further study of this three-phase system may help in the understanding of the underlying physiological mechanisms that affect the dynamics of [La] and VO2 during exercise.

Exercise↗
PubMed1987

[System analysis of the process of oxygen supply in young sportsmen during physical exercise of various intensities].

Young sportsmen were found to have nonhomogeneous and qualitatively different participation of the hemodynamic, respiratory and tissue mechanisms in formation of the oxygen supply system on discretely increasing physical exercises. In maximal exercises, the O2 utilization in tissues is the main limiting section on oxygen consumption. Mathematic formulae are suggested to estimate the volume of blood circulation per minute according to the magnitude of oxygen consumption and respiratory capacity per minute.

Adolescent↗