- 行业: Printing & publishing
- Number of terms: 178089
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- 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 intended to detect an involuntary physiological response that all persons exhibit when lying but never when telling the truth. Because there is no such specific lie response, the lie detector of popular fancy is mythological. In actual “lie protector” tests, widely used in the United States, breathing movements, blood pressure changes, and electrodermal responses are recorded on a polygraph while the respondent answers “yes” or “no” to a series of 8 to 12 questions. From the polygraph recordings, one can determine whether “relevant” questions had a greater impact on the respondent than did the interpolated “control” questions. In the standard lie test used in specific issue investigations, the relevant questions ask whether the respondent committed the act in question; for example, “On April 12, did you take $2000 from the office safe?” A typical control question might be, “In the first 20 years of your life, did you ever steal anything?” If the examinee reacts more strongly to the relevant than to the control questions, it is inferred that his or her answers to the relevant questions are deceptive. Because an innocent accused also may be disturbed by the relevant questions and react more strongly to them than to the controls, the lie test is biased against the truthful respondent. Research has shown that as many as 50% of innocent criminal suspects may “fail” control-question polygraph tests.
Industry:Science
A device or circuit that maintains a load voltage nearly constant over a range of variations of input voltage and load current. Voltage regulators are used wherever the unregulated voltage would vary more than can be tolerated by the electrical equipment using that voltage. Alternating-current distribution feeders use regulators to keep the voltage supplied to the user within a prescribed range. Electronic equipment often has voltage regulators in dc power supplies.
Industry:Science
A device or enclosure to provide thermal processing of an article or substance in a controlled temperature environment or atmosphere, often by direct firing, but occasionally by convection or radiation heat transfer. Kilns are used in many different industries, and the type of device called a kiln varies with the industry.
Industry:Science
A device that automatically measures the angular separation of stellar observations with respect to a reference platform. It is also referred to as an as-trotracker.
Industry:Science
A device that combines an electrical information signal with a periodic electrical carrier signal for efficient transmission. The modification of a usually sinusoidal electrical carrier signal (or simply carrier) for the purpose of transmitting information which 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 in order to imbed the information for efficient transmission. During the process of modulation, information is shifted in frequency from baseband to the carrier frequency for efficient transmission.
Industry:Science
A device that computes and displays speed of an aircraft relative to the air mass in which the aircraft is flying. Three common types are the indicated airspeed meter, true airspeed indicator, and Machmeter.
Industry:Science
A device that constrains or guides the propagation of electromagnetic radiation along a path defined by the physical construction of the guide. Electromagnetic waves may propagate in space, as radio waves, but for many purposes waves need to be guided with minimum loss from the generating point to a point of application. Several guiding systems are of importance, including two-conductor transmission lines, various forms of striplines used in microwave integrated circuits, hollow-pipe waveguides, and dielectric waveguides. Since transmission lines and striplines are discussed in other articles, the emphasis in this article is on hollow-pipe and dielectric guides. Hollow-pipe guides are used primarily in the microwave region of the spectrum, dielectric guides primarily in the optical region.
Industry:Science
A device that converts an analog information signal to a pulse format. A pulse modulator encodes the amplitude information at a particular time by a set of short- or long-duration pulses using such methods as pulse-amplitude, pulse-width, pulse-position, pulse-density, or pulse-code modulation. A pulse modulator, therefore, accepts a continuous analog input signal and provides a pulse output that conveys the amplitude of the continuous analog signal as seen at an observation, or sampling, time <i>t</i><sub><i>s</i></sub>, often optimistically described as a sampling instant.
Industry:Science
A device that converts an electrical signal from an amplifier into sound. A loudspeaker driver is an electromechanical-acoustic device with two electrical input terminals, to which an electrical signal is applied, and a diaphragm which vibrates and radiates sound. An electromechanical motor mechanism exerts a force on the diaphragm to cause it to vibrate. By far the most common type of motor mechanism, the electromagnetic-mechanical transducer, employs a coil of wire immersed in a magnetic field; electric current flowing through the coil causes a force to be exerted on the coil which is mechanically coupled to the diaphragm. A less common type of motor mechanism is the electrostatic-mechanical transducer. It uses a capacitor to which an electric voltage is applied, causing a force to be exerted between the capacitor plates, which is mechanically coupled to the diaphragm. Two types of electrostatic transducers are used: the piezoelectric transducer and the condenser transducer. The piezoelectric transducer uses a piezoelectric crystal between the capacitor plates. The condenser transducer uses an air dielectric. One plate of the capacitor is a flexible membrane which serves as the diaphragm.
Industry:Science
A device that converts the digital signals produced by terminals and computers into the analog signals that telephone circuits are designed to carry. Despite the availability of several all-digital transmission networks, the analog telephone network remains the most readily available facility for voice and data transmission. Since terminals and computers transmit data using digital signaling, whereas telephone circuits are designed to transmit analog signals used to convey human speech, a device is required to convert from one to the other in order to transmit data over telephone circuits. The term modem is a contraction of the two main functions of such a unit, modulation and demodulation. The device is also called a data set.
Industry:Science
