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The ratio of the current to the voltage in an alternating-current circuit.In terms of complex current I and voltageV, the admittance of a circuit is given by Eq. (1), and is related to the impedance of the circuit Z by Eq. (2). Y is a complex number…

A photograph of a portion of the Earth's surface taken from an aircraft or from a satellite. Most often, these photographs are taken sequentially and overlap each other, to give complete coverage of the area of interest. Thus they may be viewed…

The force exerted on a body whenever there is a relative velocity between the body and the air. There are only two basic sources of aerodynamic force: the pressure distribution and the frictional shear stress distribution exerted by the airflow on…

Sound that is generated by the unsteady motion of a gas and its interaction with surrounding surfaces. Aerodynamic sound or noise may be pleasant, such as the sound generated by a flute, or unpleasant, such as the noise of an aircraft on landing or…

The force retarding an airplane, especially in supersonic flight, as a consequence of the formation of shock waves. Although the physical laws governing flight at speeds in excess of the speed of sound are the same as those for subsonic flight, the…

The applied science that deals with the dynamics of airflow and the resulting interactions between this airflow and solid boundaries. The solid boundaries may be a body immersed in the airflow (Fig. 1), or a duct of some shape through which the air…

A combination of two sciences, fluid mechanics and thermodynamics. Theodore von Kármán defined aerothermodynamics in this way in the 1950s, following G. Arturo Crocco, who introduced the term in 1931. Taken literally, this term includes classical…

Aircraft specifically designed or adapted from a general utility airframe for use in agriculture and forestry and for control of insect vectors of human, animal, and plant diseases. Agricultural aircraft (Fig. 1) have become an indispensable tool…

All buildings used on the farm for housing livestock and the farm family and for storing grain, livestock feed, and farm machinery. In the United States, today's farms are larger, more specialized, and more mechanized than those of the past, and…

A discipline concerned with solving the engineering problems of providing food and fiber for the people of the world. These problems include designing agricultural machinery to work the soil and harvest the crops, as well as developing water…