Columbia Encyclopedia

Search results

500 results found

ultrasonics

(Encyclopedia)ultrasonics, study and application of the energy of sound waves vibrating at frequencies greater than 20,000 cycles per second, i.e., beyond the range of human hearing. The application of sound energy...

solid

(Encyclopedia)solid, one of the three commonly recognized states in which matter occurs, i.e., that state, as distinguished from liquid and gas, in which a substance has both a definite shape and a definite volume....

photoelectric effect

(Encyclopedia)photoelectric effect, emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory ...

Saint-Denis, city, France

(Encyclopedia)Saint-Denis săN-dənēˈ [key], city (1990 pop. 90,806), Seine–Saint-Denis dept., N central France. It is an industrial suburb N of Paris. Metals, chemicals, machinery, electronics, and food produc...

caravan

(Encyclopedia)caravan, group of travelers or merchants banded together and organized for mutual assistance and defense while traveling through unsettled or hostile country. Caravan trade is associated with the hist...

commodity market

(Encyclopedia)commodity market, organized traders' exchange in which standardized, graded products are bought and sold. Worldwide, there are more than 20 major commodity exchanges and many smaller ones that trade c...

El Paso

(Encyclopedia)El Paso ĕl păˈsō [key], city (2020 pop. 678,815), seat of El Paso co., extreme W Tex., on ...

milling

(Encyclopedia)milling, mechanical grinding of wheat or other grains to produce flour. Milling separates the fine, mealy parts of grain from the fibrous bran covering. In prehistoric times grain was crushed between ...

wire

(Encyclopedia)wire, metal filament, strand, or solid rod usually having a round cross section. Metals and alloys used for wiremaking are chosen for high tensile strength and ductility or for their electrical conduc...

3D printer

(Encyclopedia)3D printer, computerized device that produces a three-dimensional object by creating it as a series of thin layers. The object is created from a model stored in computer-aided design file; the model i...