- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- Company Profile:
McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A device that joins electrical conductors mechanically and electrically to other conductors and to the terminals of apparatus and equipment. The term covers a wide range of devices designed, for example, to connect small conductors employed in communication circuits, or at the other extreme, large cables and bus-bars.
Industry:Science
A device that makes, breaks, or changes the course of an electric circuit. Basically, an electric switch consists of two or more contacts mounted on an insulating structure and arranged so that they can be moved into and out of contact with each other by a suitable operating mechanism.
Industry:Science
A device that measures local acceleration due to the Earth's gravity; it is also called a gravimeter. Such instruments fall into two categories: relative gravity meters, which are used to determine gravity differences among a number of geographic locations or changes in gravity that occur at a single location over time; and absolute gravity meters, which can measure the true value of the acceleration due to gravity at a given location and time.
Industry:Science
A device that processes numerical information; more generally, any device that manipulates symbolic information according to specified computational procedures. The term digital computer—or simply, computer—embraces calculators, computer workstations, control computers (controllers) for applications such as domestic appliances and industrial processes, data-processing systems, microcomputers, microcontrollers, multiprocessors, parallel computers, personal computers, network servers, and supercomputers.
Industry:Science
A device that produces electrical noise for use in electrical measurements. Electrical noise generators are commonly employed to measure the noise figure or noise temperature of radio receivers. They are also used in various other tests in radar and communications systems. Celestial noise sources are used to calibrate large antennas.
Industry:Science
A device that provides the pilot with symbols representative of the attitude of an aircraft relative to an artificial horizon. In an automatic or artificial horizon a vertical gyro moves a horizon bar relative to a fixed aircraft index. Motion of the bar simulates changes in pitch or roll of the aircraft. As the indicator is viewed, the pilot sees the horizon relative to the aircraft as the horizon would appear if it could be seen through the windscreen (see <b>illus</b>.). The vertical gyro may be contained within the indicator, or it may be remote as part of a flight-director system. The gyro can be air-driven (for low-flying aircraft) or electrically driven. The display has been improved by making the space above the horizon bar blue and the area below either black, brown, or green. The aircraft marker, which was formerly a W-shaped wire, now looks much like an aircraft wing. For extreme pitch up or down, the command for the aircraft control is printed on the display as <small>DIVE</small> or <small>CLIMB</small>. Improvements resulted in optical displays created electronically to increase the information on the display. Means are also included to continuously correct the gyro for precession errors.
Industry:Science
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, levers, ratchets, and pawls perform mathematical operations—for example, the speedometer and the watt-hour meter (used to measure accumulated electrical usage). The general public has become much more aware of the digital computer with the rapid proliferation of the hand-held calculator and a large variety of intelligent devices, ranging from typewriters to washing machines, and especially with exposure to the Internet and the World Wide Web.
Industry:Science
A device that recovers from a transmitted signal information that has been embedded in the signal by a process of modulation. The modification of a usually sinusoidal electrical carrier signal (or simply carrier) for the purpose of transmitting information that is carried on a second electrical modulating signal or information signal is called modulation. The device or circuit that performs the modulation is called a modulator. The information may be from any of a variety of sources such as sensor data, speech signals, or image data. The modulator varies the carrier in amplitude, frequency, phase, or some combination to embed the information for efficient transmission. After reception, this information is recovered from the received signal by a demodulator. During modulation, information is shifted in frequency from baseband to the carrier frequency for efficient transmission. Demodulation is the reverse process by which the information is restored in frequency to its baseband.
Industry:Science
A device that recovers or detects a signal from a phase-modulated carrier. A phase-modulating (PM) signal operating on a sinusoidal carrier can be recovered in a variety of ways by phase-modulation detection (or demodulation).
Industry:Science
A device that reduces the pressure of a gas (usually air) in a container. When gas in a closed container is lowered from atmospheric pressure, the operation constitutes an increase in vacuum in this container. The unit used for vacuum is a millimeter (mm) column of mercury (Hg). Another term for the mmHg unit is the torr. These terms are used interchangeably. The torr is named in honor of E. Torricelli, a pioneer in vacuum technology. The various vacuum regions are classified asfollows: <ul><li>Low vacuum, 760 (atmospheric pressure) to 25 mmHg</li><li>Medium vacuum, 25 to 10<sup>−3</sup> mmHg</li><li>High vacuum, 10<sup>−3</sup> to 10<sup>−6</sup> mmHg</li><li>Very high vacuum, 10<sup>−6</sup> to 10<sup>−9</sup> mmHg</li><li>Ultrahigh vacuum, 10<sup>−10</sup> mmHg and beyond</li></ul> A vacuum as high as 10<sup>−15</sup> mmHg or one-billionth of a billionth of an atmosphere has been reached.
Industry:Science
