(1) Any towering structure, such as a post, which flanks an entranceway, supports power lines, marks a course for aircraft, etc. (2) A massive gateway.
Pyramid
Any huge, multi-sided solid structure with a square base and four sloping, triangular sides that meet at the top, as those built by the ancient Egyptians.
Pyramid roof
Roof having four triangular sides forming a point at the top of a pyramid. A pyramid roof is primarily used for steeples on top of churches or certain public buildings.
Pyramid zoning
Form of zoning regulation permitting all the uses permitted in more restrictive zoning to also apply to less restrictive zoning. The net effect of pyramid zoning is to pyramid only a few uses to more restrictive zoning regulations while allowing the broader base of uses to be applicable in less restrictive applications.
Pyranometer
A device used to measure total incident solar radiation (direct beam, diffuse, and reflected radiation) per unit time per unit area.
Pyrheliometer
A device that measures the intensity of direct beam solar radiation.
Pyrolysis
The transformation on a compound or material into one or more substances by heat alone (without oxidation). Often called destructive distillation. Pyrolysis of biomass is the thermal degradation of the material in the absence of reacting gases, and occurs prior to or simultaneously with gasification reactions in a gasifier. Pyrolysis products consist of gases, liquids, and char generally. The liquid fraction of pyrolisized biomass consists of an insoluble viscous tar, and pyroligneous acids (acetic acid, methanol, acetone, esters, aldehydes, and furfural). The distribution of pyrolysis products varies depending on the feedstock composition, heating rate, temperature, and pressure.
Pyroxylin
Paint or varnish binder, also called pyroxylin or nitrocellulose, which is composed from a nitric acid reaction with cellulose fibers.
Pythagorean theorem
A mathematical principal used to calculate the length of a triangle's hypotenuse where the dimensions of the other two sides are known. The square of the hypotenuse equals the sum of the squares of the other two sides.
