- 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.
An electronic instrument used to precisely measure the frequency of an input signal. Frequency counters are commonly used in laboratories, factories, and field environments to provide direct frequency measurements of various devices. The most common applications for frequency counters are measurement and characterization of oscillator and transmitter frequencies.
Industry:Science
An electronic measuring instrument which produces a display showing the relationship of two or more variables. In most cases it is an orthogonal (<i>x</i>,<i>y</i>) plot with the horizontal axis being a linear function of time. The vertical axis is normally a linear function of voltage at the signal input terminal of the instrument. Because transducers of many types are available to convert almost any physical phenomenon into a corresponding voltage, the oscilloscope is a very versatile tool that is useful for many forms of physical investigation.
Industry:Science
An electronic signal-processing technique in which a spectrum of intelligence is translated from a zero reference frequency to a higher frequency without a change of frequency relationships within the translated spectrum. Single-sideband (SSB) signals have no appreciable carrier. After translation, only the single-sideband energy remains. This form of intelligence transmission requires distortion-free amplification of the SSB signal prior to transmission and occupies only the spectrum bandwidth of that intelligence. These advantages allow SSB to be selected for communication of voice and digital data wherever there is a premium on having a minimum of transmitted power and available frequency spectrum.
Industry:Science
An electronic system which has either an instantaneous bandwidth of at least 500 MHz or a fractional bandwidth (ratio of the instantaneous bandwidth measured at the −10 dB points to the center frequency) of at least 20%, whichever is greater. Although considered a recent breakthrough in broadband wireless technology, UWB has now experienced over 40 years of technology development.
Industry:Science
An electronic-mechanical device, also called a teleprinter, for preparing, storing, transmitting, and receiving messages over a telegraph or data communication circuit. The term teletypewriter was used first for teleprinters utilized in teletypewriter exchange (TWX) service in the early 1930s. It was later applied to terminals used in other services, and became interchangeable with the terms teleprinter and printing telegraph terminal. A generic term, it should be used instead of Teletype, which is a registered trademark of the AT&T Teletype Corporation. Teletypewriters were invented by several individuals in the early 1900s, initially being adaptations of the commercial typewriters of the day. Relays, magnets, and solenoids were added to provide telegraph signal generation from the operation of the typewriter keyboards, and caused the typebaskets or typewheels to print automatically on sheets of paper.
Industry:Science
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 may also be recorded on a video tape recorder for playback at a later time.
Industry:Science
An electrostatic field with axial or plane symmetry which acts upon beams of charged particles of uniform velocity as glass lenses act on light beams. The action of electrostatic fields with axial symmetry is analogous to that of spherical glass lenses, whereas the action of electrostatic fields with plane symmetry is analogous to that of cylindrical glass lenses. Plane symmetry as used here signifies that the electrostatic potential is constant along any normal to a family of parallel planes.
Industry:Science
An element is a substance made up of atoms with the same atomic number. Some common elements are oxygen, hydrogen, iron, copper, gold, silver, nitrogen, chlorine, and uranium. Approximately 75% of the elements are metals and the others are nonmetals. Most of the elements are solids at room temperature, two of them (mercury and bromine) are liquids, and the rest are gases.
Industry:Science
An element of a mechanical linkage. A link may be a straight bar or a disk, or it may have any other shape, simple or complex. It is assumed, for simple analysis, to be made of unyielding material; that is, its shape does not change. The frame, or fixed member, of a linkage is one of the links, whether the frame is fixed relative to the Earth or relative to a movable body such as the chassis of an automobile.
Industry:Science
An element which exhibits the external characteristics of a metal but behaves chemically both as a metal and as a nonmetal. Arsenic and antimony, for example, are hard crystalline solids that are definitely metallic in appearance. They may, however, undergo reactions that are characteristic of both metals and nonmetals. Certain of their oxides dissolve in either acids or bases, and are said to be amphoteric in character because they behave either as a base or an acid. Many elements form compounds that are amphoteric. However, only when this dualistic chemical behavior is very marked and the external appearance metallic is the element commonly called a metalloid.
Industry:Science
