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Complex systems in which computers play a major role. While complex physical systems and sophisticated software systems can help people to lead healthier and more enjoyable lives, reliance on these systems can also result in loss of money, time, and…

The simultaneous execution of several interrelated computer programs. A sequential computer program consists of a series of instructions to be executed one after another. A concurrent program consists of several sequential programs to be executed in…

A directional antenna consisting of the combination of a reflector comprising two conducting planes forming a dihedral angle and a driven radiator or dipole which usually is in the bisecting plane. It is widely used both singly and in arrays, gives…

A large, tawny brown wild cat, Puma concolor (family Felidae), once widespread over most of the Americas; also known as catamount, mountain lion, painter, and puma. The cougar (Puma concolor; see illustration) is a carnivorous member of the family…

Interference in a communications channel (disturbed channel) caused by activity in other communications channels (disturbing channels). The term was originally used to denote the presence in a telephone receiver of unwanted speech signals from other…

An extremely diverse, species-rich group of arthropods that have inhabited marine environments since the beginning of the Cambrian Period. Crustacea is a notable taxon of invertebrates. Common members of the Crustacea, that is, crustaceans, are…

The Southern Cross, a small southern constellation. Because of the absence of a star at the center of the cross, this constellation really looks like a kite (see illustration). To its side, the Coalsack is a giant dark silhouette of dust against the…

The various mechanisms for data confidentiality, data authentication, and nonrepudiation (that is, the property to prevent the denial of previous commitments or actions). Cryptography, with a long history of being an art of secret writing, has…

A class of the phylum Cnidaria, comprising the box jellyfish. Members of the Cubozoa are commonly known as box jellyfish or cubozoans. These cnidarian invertebrates are good swimmers, and their distribution is mostly tropical and subtropical. There…

The exchange of data between two devices over a communications medium. The development of data communications and networking technologies has had a profound impact on all aspects of modern life. Arguably, no other technology has affected more people…