P glossary entries

The Pareto front is the image in objective space of the set of all Pareto-optimal solutions to a multi-objective optimization problem — the boundary beyond which no objective can be improved without degrading at least one other.

The Paris–Erdogan law is an empirical power-law relationship that describes the stable crack growth rate per fatigue cycle as a function of the range of the stress intensity factor at the crack tip.

The principle that pressure applied to a confined fluid is transmitted undiminished throughout the fluid.

Patient safety is the engineering and clinical outcome of reducing avoidable harm to patients during diagnosis, monitoring, treatment, support, or care delivery.

A measure of how easily a fluid, magnetic field, or other quantity passes through a material.

A frequency-domain stability margin measuring additional phase lag required to reach instability.

A photodiode is a semiconductor device that converts incident photons into electrical current through the photoelectric effect.

Physiological monitoring is the measurement and interpretation of biological or patient signals over time.

A PID controller is a feedback controller that computes its output as the weighted sum of three terms derived from the error signal: a proportional term, an integral term, and a derivative term.

The coupling between mechanical strain and electric charge in certain materials.

Plasma is an ionized gas containing free electrons, ions, neutral particles, and electromagnetic fields.

Plastic deformation is permanent deformation that remains after applied stress is removed because the material has exceeded its elastic range.

Poisson's ratio is the negative ratio of transverse strain to axial strain for a material loaded within its linear elastic range.

Pollutant load is the mass of a pollutant entering, leaving, generated in, or removed from a system over a defined basis.

Power is the rate at which energy is transferred, converted, or dissipated per unit time.

Power factor is the dimensionless ratio of active power to apparent power in an AC circuit; for sinusoidal voltage and current it equals the cosine of the phase angle between them.

Power usage effectiveness is a data center efficiency metric equal to total facility power divided by IT equipment power.

A container designed to hold gases or liquids at pressure substantially different from ambient pressure.

A function describing the relative likelihood of a continuous random variable taking values.

A valve whose opening or flow command varies continuously with a control signal.