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Using traditional welding methods, rocket engine nozzles and combustion chambers are some of the most difficult parts to fabricate, requiring up to a year to produce a single part. Now, however, the U.S. National Aeronautics and Space Administration…

The technique of measuring the magnitude and direction of acceleration. Measurement of acceleration (see illustration) includes translational acceleration with tangential and radial components and angular acceleration. Acceleration The May 16, 2011…

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…

There is a growing body of evidence that many of the thousands of prescription and over-the-counter medications ultimately make their way into water bodies and drinking-water supplies. Typical wastewater treatment plants may not be effective at…

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…

Microplastics are raining down on national parks and other protected areas in the western United States at the rate of about 132 pieces of microplastic per square meter every day, according to a report in the journal Science (June 2020).…

Any compound having highly basic properties, strong acrid taste, and ability to neutralize acids. Aqueous solutions of alkalies are high in hydroxyl ions, have a pH above 7, and turn litmus paper from red to blue. Caustic alkalies include sodium…

A metal product containing two or more elements as a solid solution, as an intermetallic compound, or as a mixture of such metallic and/or nonmetallic phases. This article will describe alloys on the basis of their technical applications. Alloys may…

Substances formed by the addition of one or more elements, usually metals, to aluminum. The principal alloying elements in aluminum-base alloys are magnesium (Mg), silicon (Si), copper (Cu), zinc (Zn), and manganese (Mn). In wrought products, which…

Although asphalt (also known as bitumen) is a naturally occurring substance found in deposits within the earth, it is also a by-product of petroleum processing. Almost all the bitumen used for asphalt pavement and roofs comes from petroleum refining…

The engineering aspects of flight and navigation in space. Astronautical engineering deals with vehicles, instruments, and other equipment used in space (see illustration), but not with the sociological or economic aspects of space flight, except as…

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 sound-reproducing system in which sound is recorded or transmitted by using two microphones mounted at the ears of a dummy human head. To preserve the binaural effect, the sound must be monitored by a listener wearing a set of earphones…

Many questions concerning the sustainable production of biofuels have emerged over recent years in terms of land and water use, pollution from fertilizer and pest-control chemicals, greenhouse-gas production, net energy production, and whether…

The application of principles from applied and physical sciences to problems in healthcare and biology. As a field, biomedical engineering draws from a variety of disciplines including mechanical, chemical, electrical, and computer engineering, as…

In glass blowing, a long straight tube on which molten glass is gathered and worked, partly by blowing into the tube. The blowpipe (see illustration) is spun to shape the glass object further by centrifugal force, or by a tool, in which case the…

A pressurized system in which water is vaporized to steam, the desired end product, by heat transferred from a source of higher temperature, usually the products of combustion from burning fuels. Steam thus generated may be used directly as a…

A component of a steam-generating unit that absorbs heat from the products of combustion after they have passed through the steam-generating and superheating sections. The name, accepted through common usage, is indicative of savings in the fuel…

Water supplied to a boiler for the generation of steam. The water is heated to produce steam and acts to cool the heat-absorbing surfaces as it circulates through the boiler. The steam withdrawn from the steam drum is of high purity, and…

Addition of water to a steam-generating unit at a rate commensurate with the removal of steam from the unit. The addition of water to a boiler requires a feedwater pump or some other device that will develop a pressure higher than that of the steam…

A device for detecting and measuring small amounts of thermal radiation. The bolometer is a simple electric circuit, the essential element of which is a slab of material with an electrical property, most often resistance, that changes with…

A cylindrical fastener with an integral head on one end and an external screw thread on the other end designed to be inserted through holes in assembled parts and to mate with an internally threaded block, called a nut, which is turned to tighten or…

An assembly of two or more parts fastened together by inserting bolts through matching clearance holes in the parts and engaging nuts that are then tightened to clamp the assembly. The term bolted joint also colloquially denotes a screwed joint, for…

A method of holding the parts of an object together with or without the aid of an adhesive such as an epoxy or a glue. Composite materials such as fiber-reinforced plastics require strong interfacial bonding between the reinforcement and the matrix.…

A subprocess of welding encompassing a group of process embodiments in which coalescence is produced by heating to suitable temperatures above 450°C and by using a filler metal that must have a liquidus temperature above 450°C and below the solidus…

Assembling an electronic circuit in the most convenient manner on a board or other flat surface, without regard for final locations of components, to prove the feasibility of the circuit and to facilitate changes when necessary. Standard breadboards…

The potential difference at which an electrically stressed gas is tranformed from an insulator to a conductor. In an electrically stressed gas, as the voltage is increased, the free electrons present in the gas gain energy from the electric field.…

A circuit composed of a source and four impedances that is used in the measurement of a wide range of physical quantities. The bridge circuit is useful in measuring impedances (resistors, capacitors, and inductors) and in converting signals from…

Electronic circuits whose primary function is to connect a high-impedance source to a low-impedance load without significant attenuation or distortion of the signal. Thus, the output voltage of a buffer replicates the input voltage without loading…

The resultant vertical force exerted on a body by a static fluid in which the body is submerged or floating. Buoyancy is the upward force exerted by a fluid (liquid or gas) on a body that is placed within it (see illustration). The buoyant force FB…

The velocity at which the combustible gases move through a flame in the direction perpendicular to the flame surface defines the burning velocity. The term flame as used here refers to the burning of combustible gases. The process of combustion, or…

An aluminum or copper conductor supported by insulators that interconnects the loads and the sources of electric power in an electric power system. A typical application is the interconnection of the incoming and outgoing transmission lines and…

A removable metal lining, usually in the form of a bearing to carry a shaft. Generally a bushing is a small bearing in the form of a cylinder and is made of soft metal or graphite-filled sintered material. Bushings are also used as cylindrical…

The testing of electric circuits to determine and locate any of the following circuit conditions: (1) an open circuit, (2) a short circuit with another conductor in the same circuit, (3) a ground, which is a short circuit between a conductor and…

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 broad designation for a class of solid carbon-based materials with high elemental carbon content produced from the thermal decomposition of hydrocarbons. Carbon black can be produced with a range of physical properties tailored to applications.…

An amplifier stage consisting of a common-emitter transistor cascaded with a common-base transistor. The common-emitter–common-base (CE-CB) transistor pair constitutes a multiple active device which essentially corresponds to a common-emitter stage…

Catenanes are compounds that are made of interlocking macrocycles. The interlocking rings are said to be mechanically rather than chemically bound. Catenanes are named according to the number of interlocking rings. The simplest catenane, containing…

The name given to the electrons originating at the cathodes of gaseous discharge devices. The term has now been extended to include low-pressure devices such as cathode-ray tubes. Furthermore, cathode rays are now used to designate electron beams…

An electron tube in which a beam of electrons can be focused to a small cross section and varied in position and intensity on a display surface. In common usage, the term cathode-ray tube (CRT) is usually reserved for devices in which the display…

A luminescence resulting from the bombardment of a substance with an electron (cathode-ray) beam. The principal applications of cathodoluminescence are in television, computer, radar, and oscilloscope displays. In these a thin layer of luminescent…

The formation of vapor- or gas-filled cavities in liquids. If understood in this broad sense, cavitation includes the familiar phenomenon of bubble formation when water is brought to a boil under constant pressure and the effervescence of champagne…

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…

Light emitted by a high-speed charged particle when the particle passes through a transparent, nonconducting, solid material at a speed greater than the speed of light in the material. The blue glow observed in the water of a nuclear reactor, close…

A flexible device of connected links used to transmit power. A drive consists of an endless chain which meshes with sprockets located on the shaft of a driving source, such as an electric motor/reducer, and a driven source, such as the head shaft of…

A single-particle detector which in its basic form (Fig. 1) consists of a hollow tube (channel) of either glass or ceramic material with a semiconducting inner surface. The detector responds to one or more primary electron impact events at its…

Semiconductor devices wherein minority charge is stored in a spatially defined depletion region (potential well) at the surface of a semiconductor, and is moved about the surface by transferring this charge to similar adjacent wells. The formation…

The branch of physics concerned with the motion of charged particles under the influence of electric and magnetic fields. Acceleration of charged particles A positively charged particle that moves in an electric field experiences a force in the…

A chemical manufacturing process in which chemical transformation takes place, that is, the product differs chemically from the starting materials. Most chemical manufacturing processes consist of a sequence of steps, each of which involves making…

A process used to purify substances or to isolate them from other substances. In industrial applications, the ultimate goal is the isolation of a product of given purity. Most industrial chemical processes involve a separation stage. This may…

A law governing space-charge-limited flow of electron current between two plane parallel electrodes in vacuum when the emission velocities of the electrons can be neglected. It is often called the three-halves power law, and is expressed by the…

An inductor that is used to prevent electric signals and energy from being transmitted along undesired paths or into inappropriate parts of an electric circuit or system. Power-supply chokes prevent alternating-current components, inherent to a…

The act of interrupting an electric current, beam of light, or beam of infrared radiation at regular intervals. This can be accomplished mechanically by rotating a vibrating mirror in the path of the beam to deflect it away from its intended source…

Any device that measures a time interval. The term is usually restricted to measurements that have a small percentage error. Early time measurements used the human pulse rate or counted the number of swings of a pendulum for small time intervals.…

A large, strongly built watch especially designed for precise timekeeping on ships at sea. The name is sometimes loosely applied to any fine watch. WatchThe features that distinguish a chronometer from a watch are (1) a heavy balance wheel, the axis…

A general term referring to a system or part of a system of conducting parts and their interconnections through which electric currents are intended to flow. A circuit is made up of active and passive elements or parts and their interconnecting…

An interconnection of electronic devices, an electronic device being an entity having terminals which is described at its terminals by electromagnetic laws. Most commonly these are voltage–current laws, but others, such as photovoltaic…