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A conductor whose purpose is to emit and/or receive electromagnetic waves using the bulk oscillations of electric charges within the conductor. The conduction electrons in antennas are free to move throughout the conductor. The electrons form a bulk…

The subfield of computer science concerned with understanding the nature of intelligence and constructing computer systems capable of intelligent behavior. Many activities, such as perception, learning, planning, natural language, and understanding,…

Cameras in mobile phones or smartphones that can capture images and videos.The cellphone, the world’s favorite must-have gadget, has been with us for nearly a half-century, while experiencing continuous and often phenomenal improvements. Much of the…

A branch of computer science that deals with the theory and techniques of computer-generated images. Computers produce images by analyzing a collection of dots, or pixels (picture elements). Computer graphics is used to enhance the transfer and…

A radar system used to measure the relative velocity of targets and their position. The operation of these systems is based on the fact that the Doppler frequency shift in the target echo is proportional to the radial component of target velocity.…

An interdisciplinary science area that is concerned with modeling aspects of natural evolution in order to solve real-world problems of optimization. Living organisms, as well as those that are long extinct, demonstrate optimized complex behavior at…

The evolving internet technologies for content sharing and collaborating among communities of online users. Since the advent of the Web 2.0—the more dynamic and interactive second generation of the World Wide Web—the term social media has become…

The theory of circuits made up of ideal digital devices. Included in switching theory are the theories of circuits and networks for telephone switching, digital computing, digital control, and data processing. Computer Electrical circuit Electronic…

A management technology involving the interactions of science, an organization, and its environment as well as the information and knowledge that support each. The purpose of systems engineering is to support organizations that desire improved…

A process of making physical objects directly from digital models, usually layer by layer; also known as additive manufacturing (AM). 3D printing has been hailed by many as the technology that will revolutionize how we live. As information…

Mechanized systems of food and fiber production used in agriculture. The mechanized systems comprising agricultural machinery are utilized in numerous aspects of agriculture, including the initial tillage of the soil (Fig. 1), planting, cultural…

A small, tropical, evergreen tree (Pimenta dioica) and its dried, unripe fruit (berry). Allspice (Pimenta dioica; alternatively, P. officinalis) [see illustration] is a member of the myrtle family (Myrtaceae). Allspice, which is also known as…

Any vegetable that is prevalent in Asian cuisines, but less well known in Western diets. Asian vegetables (Fig. 1), also referred to as Asian greens or oriental vegetables, are very important in Asian countries, but are not as popular in North…

A discipline that combines biology, mathematics, and computer science to acquire, store, analyze, and disseminate complex biological data. The term bioinformatics was coined by Paulien Hogeweg and Ben Hesper in the early 1970s to describe the "the…

A medium-sized, spreading evergreen tree (Anacardium occidentale), which is grown widely in the tropics for its kidney-shaped edible nuts (also called cashews) and the resinous oil in the shells of the nuts. Cashew trees, which are native to Brazil,…

Any member of the grass family (Poaceae or Gramineae) that produces edible grains usable as food by humans and livestock. Cereals are important cultivated crops. Common cereals include rice, wheat, barley, oats, maize (corn), sorghum, rye, and…

An evergreen shrub or small tree, particularly Cinnamomum verum, and the spice obtained from the plant's bark. The cinnamon plant (see illustration) is a member of the laurel family (Lauraceae) in the order Laurales. Native to Sri Lanka, the…

A device that receives, processes, and presents information. The two basic types of computers are analog and digital. Although generally not regarded as such, the most prevalent computer is the simple mechanical analog computer, in which gears,…

Any device connected internally or externally to a computer and used in the transfer of data to or from a computer. A personal computer (PC) processes information. Data (unprocessed information) must get into the computer, and the processed…

Designing and writing a detailed sequence of operating instructions for a particular problem to be run on a computer; also known as programming. A computer is able to perform useful tasks only by executing computer programs. A programming language…

The process of protecting against threats to computing systems. A threat is an event that can cause harm to computers, data or programs, or computations (Fig. 1). A failure of computer security occurs because of a vulnerability or weakness in a…

The hardware components, both internal and external, of a computer used to read (retrieve) or write (save) digital data. The ability to read and write data is an essential function of a computer and of the so-called von Neumann architecture…

A program or script that is loaded and executed on a computer without the knowledge of the user. A typical computer virus is a very small program, several kilobytes or less in size, constructed in a matter of hours or days. When executed, the virus…

The technology concerned with computational understanding and use of the information present in visual images. In part, computer vision is analogous to the transformation of visual sensation into visual perception in biological vision. For this…

A digital equivalent of paper banknotes. Just like paper banknotes, cryptocurrencies allow users to maintain privacy in digital commercial transactions while ensuring that value is transferred from one party to the other. Cryptocurrencies achieve…

The computer manipulation of visual data to solve a problem. The problems under consideration are of two primary types: (1) those that require a computer to act on the resultant images, and (2) those that provide images for human interpretation. The…

Programmable computers integrated with electrically powered machines that perform household chores. Domestic robots, also known as home or service robots, are essentially programmable computers integrated with electrically powered machines that…

The manner in which electromagnetic waves travel forward along a path. Electromagnetic waves consist of quantized, traveling, self-sustained, electromagnetic field fluctuations. The high speed of electromagnetic waves makes them useful in…

A System that locates suitably equipped users by means of measurements made by electronic sensors. Typical measurements include distance or bearing from a vehicle to a known point, or direct determination of the present position of the vehicle in a…

An enzymatic transformation of organic substrates, especially carbohydrates, generally accompanied by the evolution of a gas. Fermentation is a chemical transformation of organic substrates, especially carbohydrates, to alcohol or organic acids,…

The application of different types of energy and techniques involving equipment and apparatuses to transform agricultural products of plant and animal origin or seafood into food ingredients, semifinished commodities, and finished ready-to-eat…

The study of the physical, chemical, and biological properties of foods as well as the sensory, nutritional, storage properties, and safety of foods. Food properties are influenced by growing, harvesting, and slaughtering practices, preservation and…

Any of the grasses and legumes that make up grasslands and are consumed by grazing livestock. Grasslands represent an ancient renewable natural resource. In general, grasslands form 25% of the world's vegetation and occupy the largest area of any…

A hardy perennial, Allium sativum, of Asiatic origin and belonging to the plant order Asparagales. Garlic is grown for its pungent bulbs (see illustration). Segments of these are used primarily for seasoning. Europeans have grown garlic for probably…

An important spice or condiment, and the plant (Zingiber officinale) from which it is obtained. The ginger plant, Zingiber officinale, is a member of the ginger family Zingiberaceae and is a native of southeastern Asia. The plant is an erect…

Any of the crop plants belonging to the grass family (Poaceae or Gra­mineae) that are generally grown for their edible starchy seeds. Grain crops are often referred to as cereal crops and include wheat, rice, corn (maize), barley (see illustration),…

The responsible use of computer and related resources with the objective of curbing the negative effects that the increasing use of computers and their associated technologies have on the Earth's limited natural resources. Green computing is part of…

An uncrewed, controlled-flight vehicle that is guided to a target by guidance and control equipment. This equipment may be carried in the missile vehicle itself, or guidance may be directed from the launch site. The term is generally reserved for…

Optical instruments that establish an optical line or axis for the purpose of aiming a weapon. The axis includes the observer's eye, a suitable mark in the instrument, and the target. For a pistol, the traditional iron sights employ a rear notch and…

An intensively managed plant cultivated for food or for esthetic purposes. Plant agriculture is divided traditionally into the fields of agronomy (herbaceous field crops, mainly grains, forages, oilseeds, and fiber crops), forestry (forest trees and…

An interdisciplinary field focused on the interactions between human users and computer systems, including the user interface and the underlying processes that produce the interactions. The contributing disciplines include computer science,…

The field of engineering involving computer-based hardware and software systems, and communication systems, to enable the acquisition, representation, storage, transmission, and use of information. Information technology (IT) is critically dependent…

Intentional generation of interfering signals in the electromagnetic spectrum by powerful transmitters as a countermeasure intended to block a communication, radar, or infrared system or to impair its effectiveness appreciably. Radio broadcasts or…

Solvent removal from the frozen state by sublimation; commonly referred to as freeze-drying. In lyophilization, the dried material, a porous solid, is sealed under vacuum or inert-gas (liquid nitrogen) atmosphere and retains its physical and…

A branch of artificial intelligence (AI) based on the notion that machines (software applications) can learn from examples and can teach themselves how to solve specific problems without being programmed manually. Recent successes in artificial…

Weapons that arm warships. Of the wide variety of such weapons, three important categories are exclusively naval: antiship missiles, torpedoes, and mines. Other weapons all correspond to land-based types, but submarine-launched ballistic missiles…

The cultivation of plants, primarily trees, that produce nuts. The term nut is used loosely. In general, a nut is defined as any edible fruit or seed enclosed in a hard shell. Botanically, a nut is a hard, indehiscent, one-seeded (nut), pericarp…

A delicately flavored spice obtained from the nutmeg tree (Myristica fragrans), a native of the Moluccas (Maluku Islands or Spice Islands). The nutmeg tree is a dark-leafed evergreen that can reach 9–18 m (30–60 ft) in height and is a member of the…

Any plant of the genus Olea in the order Lamiales (alternatively Scrophulariales), especially O. europaea, which is cultivated for its drupaceous fruit. Olea europaea is a small to medium-sized evergreen tree (Fig. 1). Olive fruits, both ripe…

Computer software that is licensed by the copyright holder, granting the rights to examine, change, and distribute it to anyone and for any purpose as long as the original copyright statement in any redistributed software is preserved. The…

A type of pepper, Capsicum annuum, with nonpungent flesh, grown for its long red fruit. The paprika pepper (see illustration) is a member of the plant order Solanales (formerly assigned to Polemoniales) and is of American origin. It is most popular…

The mint species Mentha piperita in the family Lamiaceae (Labiatae). Peppermint (see illustration) is a sterile interspecific hybrid that is believed to have occurred in nature from the hybridization of fertile Mentha aquatica with fertile Mentha…

The notation used to communicate instructions to a computer. A computer executes a sequence of instructions (a program) in order to perform some task. The set of instructions and the order in which they have to be performed is known as an algorithm.…

The means by which radio waves move from one place to another. A radio wave is an electromagnetic wave that has a frequency within the radio-frequency spectrum, from 3 kHz (3000 Hz, where Hz is the symbol for hertz, a unit of frequency defined as…

Brassica napus, a plant of the cabbage family. Rape (Brassica napus) [see illustration] and turnip rape (B. rapa or B. campestris), which are closely related, are members of the Brassicaceae (Cruciferae) plant family [order Brassicales or…

A set of instructions that causes a computer to perform one or more tasks. The set of instructions is often called a program or, if the set is particularly large and complex, a system. Computers cannot do any useful work without instructions from…

The production of software through a progression of disciplined and controlled steps. As the need for complex, real-time, and life-critical software proliferates, there is a demand for an effective software development process that guarantees the…

Mentha spicata, an aromatic, vegetatively propagated, clonal cultivar species of the mint family Lamiaceae (Labiatae). The leaves of the spearmint plant are used as a flavoring in foods. In many areas, the mint is grown primarily as a source of the…

A device that automatically measures the angular separation of stellar observations with respect to a reference platform. It is also referred to as an astrotracker.By utilizing the star tracker in conjunction with a precise time reference…

A hissing, crackling, or other sudden sharp noise that tends to interfere with the reception, utilization, or enjoyment of desired signals or sounds. Perhaps the commonest form of static is that heard in ordinary broadcast receivers during…

The transmission of stereophonic audio signals over broadcast radio systems, including terrestrial analog amplitude-modulation (AM), frequency-modulation (FM) systems, and digital radio systems (terrestrial and satellite). Stereophonic…

A cable laid on the ocean floor to transmit signals. The challenge for submarine cables has been to convey signals long distances under water where there is no opportunity for easy access at intervening points. In the 1850s these were direct-current…

Any of the crops produced as major sources of sugar, syrup, and other sugar substances. Sugar crops include sugarbeet (also spelled sugar beet), sugarcane (Fig. 1), sweet sorghum, sugar maple, sugar palm, honey, corn, and chicory. Sugar is a broad…

A member of the rho-theta family of air navigation systems which define an aircraft's position by its distance and bearing to a single beacon. Such systems inherently answer the navigator's questions of “in what direction” and “how far,” without…

In a broad sense, teleconferencing encompasses the various ways and means by which people communicate with one another over some distance. In a narrow sense, a teleconference is a two-way, interactive meeting among individuals or relatively small…

A method of communication employing electrical signaling impulses produced and received manually or by machines. Telegraph signals are transmitted over open wire or cable land lines, submarine cables, or radio. Telegraphy as a communication…

The branch of engineering, also called telemetry, which is concerned with collection of measurement data at a distant or inconvenient location, and display of the data at a convenient location. One example of a complex telemetering system is used to…

A handheld device that permits communication over a network between persons who are in different locations. A traditional telephone instrument, also called a set, contains a transmitter for converting the acoustic signals of a person's voice to…

The technology of providing many types of communications services via networks that transmit voice, data, image facsimile, and video by using both analog and digital encoding formats. Component sectors and core technologies Telephone services…

Construction of the physical components of the telephone system from the central office to the end user. The telephone system can be roughly divided into three major components: outside plant, switching equipment, and interoffice facilities. The…

The electrical transmission and reception of transient visual images. Like motion pictures, television consists of a series of successive images which are registered in the brain as a continuous picture because of the persistence of vision. Each…

An electrooptical system used to pick up and convert a visual image or scene into an electrical signal called video. The video may be transmitted by cable or wireless means to a suitable receiver or monitor some distance from the actual scene. It…

Arrangements of communications channels, suitable for transmission of video and accompanying audio signals, which link together groups of television broadcasting stations or closed-circuit television users in different cities so that programs…

The process used to convert a three-dimensional image intensity into a one-dimensional television signal waveform. The image information captured by a television camera conveys color intensity (in terms of red, green, and blue primary colors) at…

The accepted criteria for a television system, including the image aspect ratio, number of lines per frame, type of scanning, original video signal bandwidth, transmission format and bandwidth, reception, demodulation, decoding, and sound system.…

A facility designed for the production of television programs, which may be broadcast live concurrently with the production or recorded for later broadcast. A television studio consists of the studio room, wherein the actual program takes place, and…

Any of a large and diverse group of perennial plants in the genus Thymus (order Lamiales), whose essential oil and leaves are utilized in cooking and medicine. Hundreds of different forms, or ecotypes, of thyme are found in the Mediterranean area,…

An electronic display that allows a user to interact with a computer system by touching an area or areas on the display. Touch-screen displays have been in use for many years in ATMs, checkout registers, and other applications, but gained mass…

A cereal grass plant (× Triticosecale) obtained from the hybridization of wheat with rye. Triticale (Fig. 1) is a crop plant with a small-seeded cereal grain that is used for human food and livestock feed. Plant breeders developed triticale by…

Electronic systems that transmit radio-frequency (RF) energy with either (1) an instantaneous bandwidth of at least 500 MHz, or (2) a 10-dB fractional bandwidth (ratio of the instantaneous bandwidth measured at the –10 dB points to the center…

The second generation of the World Wide Web (WWW), which is more dynamic and interactive than its predecessor, Web 1.0. Although the term Web 2.0 follows the trend to number the new releases or versions of software products, in reality the term is…

A collective name for those fungi that possess, under normal growth conditions, a vegetative body (thallus) consisting, at least in part, of simple, single cells. Yeasts are a phylogenetically diverse group of organisms that occur in two divisions…

An early mechanical calculator. The abacus likely originated in Babylonia sometime before 1000 BCE. Over the subsequent centuries, it became a commonplace device in many regions of the world. The abacus is still occasionally used as a cognitive…

A discipline that deals generally with the extraction of information from acoustic signals in the presence of noise and uncertainty. Acoustic signal processing has expanded from the improvement of music and speech sounds and a tool to search for oil…

A group of software development methods in which requirements and solutions evolve through collaboration between the developers and the customers. Agile methods have significantly changed the practice of software development since their inception…

A discipline that combines the means to know the location and heading of an aircraft with respect to some map or coordinate system, with guidance which means steering the aircraft along some desired path toward a destination. The construction of the…

A white, crystalline compound, 1-aspartyl-1-phenylalanine methyl ester (APM), used as an artificial sweetener. Aspartame is composed of two amino acids: aspartic acid and phenylalanine [structure (1)]. Amino acid Artificial sweetener Aspartame…

A weapon that consists of integral rocket propulsion, means of pointing or guiding the weapon's velocity vector to a prescribed orientation at the position and time of rocket engine shutoff or burnout, and a warhead. In certain applications, means…

A fermented beverage produced from grain. Beer is a generic term used to describe alcoholic beverages made from cereal grains, especially barley (Fig. 1), in the form of malt. Ale, lager, porter, and stout are different kinds of beer made by…

A binary digit. In the computer, electronics, and communications fields, “bit” is generally understood as a shortened form of “binary digit.” In a numerical binary system, a bit is either a 0 or 1. Bits are generally used to indicate situations that…

A system that receives and processes television signals, as well as other digital forms of communications such as those related to high-speed Internet connectivity and cable telephony, from various sources and retransmits these signals through…

An electronic device that performs arithmetic, statistical, or other, more complex processing operations at the step-by-step direction of the user or by execution of a program (a stored sequence of processing operations) selected and initiated by…

A method of gathering best practices for various work processes into coherent groupings to facilitate quality and process improvement. Capability Maturity Models® (CMM®) represent a relatively recent step in the evolution of process improvement…

A periodic waveform upon which an information-bearing signal is impressed. This process is known as modulation and comprises a variety of forms such as amplitude, phase, and frequency modulation. The most common type of carrier is the sinusoidal…

A cellular automaton is a hypothetical computer constructed of a regular array of cells that interact with neighboring cells according to a set of simple rules. Though conceptually simple, cellular automata can produce complex and surprising…

A computing system that is composed of two logical parts: a server, which provides services, and a client, which requests them. The two parts can run on separate machines on a network, allowing users to access powerful server resources from their…

A service, primarily for deaf people, that allows individual viewers to display the dialog of a television program in a readable form on the television screen. In the United Kingdom the service is called subtitling. Closed-caption television was…

The use of video cameras to transmit a signal to a particular limited audience at one or more specific locations via coaxial cables, telephone wires, fiber-optic strands, microwave radio systems, or communications satellites, as compared to openly…

An electrical transmission line comprising an inner, central conductor surrounded by a tubular outer conductor. The two conductors are separated by an electrically insulating medium which supports the inner conductor and keeps it concentric with the…

Products derived from the seeds of the tropical tree Theobroma cacao. The cacao tree (Fig. 1) grows within a narrow belt along both sides of the Equator. There are three basic varieties: Criollo, which was native to Central and South America;…