- 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 tropical grass, <i>Cymbopogon nardus,</i> from the leaves of which oil of citronella is distilled. This essential oil is pale yellow, inexpensive, and much used in cheap perfumes and soaps. It is perhaps best known as an insect repellent. A large acreage is devoted to the cultivation of this grass in Java and Ceylon.
Industry:Science
A tubuloalveolar or acinous skin gland, also known as the tear gland. The lacrimal glands develop from the skin epithelium which folds inward over the developing eye. Two types occur among the vertebrates, the lacrimal proper and the Harderian. These eye glands are first found in the amphibians, associated with the inside of the lower eyelid. In urodele amphibians the eye gland extends along the inner aspect of the lower eyelid. In <i>Salamandra</i> it becomes divisible into an anterior Harderian gland associated with lower eyelid structures and a posterior lacrimal gland below the upper eyelid. In frogs and toads only the Harderian gland is present and is associated with the nictitating membrane or third eyelid which develops in relation to the lower lid.
Industry:Science
A tuned amplifier that amplifies the signals commonly used in radio communications. Amplifier designs in the radio-frequency (RF) range differ significantly from conventional low-frequency circuit approaches; they consequently require special, distributed circuit considerations. The need for a distributed treatment is warranted whenever the size of the physical circuit is greater than about one-tenth of the signal wavelength.
Industry:Science
A two- or three-wheeled self-propelled motor vehicle. Power is usually supplied by an internal combustion engine of one or more cylinders with either air or liquid cooling, although electric-powered motorcycles have been built. Transmissions commonly have four or five forward speeds; motorcycles with automatic transmissions have been commercially available, but have not achieved great popularity. Some three-wheeled motorcycles are equipped with a reverse gear. Power is transmitted from the transmission to the rear wheel by either a roller chain, a belt, or a shaft drive.
Industry:Science
A two-dimensional diagram used extensively in astronomy, developed independently by Ejnar Hertzsprung in 1911 and Henry Norris Russell in 1913. In its original form, the Hertzsprung-Russell (H-R) diagram was a plot of absolute visual magnitude versus spectral type (O, B, A, and so on). Variants are now commonly used, avoiding requirements of and uncertainties due to spectral classification. The vertical axis of the diagram is some suitable measure of the power output of the star, while the horizontal axis indicates the temperature (or color) of the star's visible surface, or the corresponding spectral type. Each point in the plot represents a nearby star of known distance. In any of its forms, the diagram reveals the most fundamental correlation among observed stellar properties discovered to date.
Industry:Science
A two-dimensional geometric figure (a collection of points) in three-dimensional space. The simplest example is a plane—a flat surface. Some other common surfaces are spheres, cylinders, and cones, the names of which are also used to describe the three-dimensional geometric figures that are enclosed (or partially enclosed) by those surfaces. In a similar way, cubes, parallepipeds, and other polyhedra are surfaces. Often only the context indicates whether a surface or a solid is being referred to, but in modern mathematical usage such words refer only to surfaces.
Industry:Science
A two-terminal electron device exhibiting a nonlinear current-voltage characteristic. Although diodes are usually classified with respect to the physical phenomena that give rise to their useful properties, in this article they are more conveniently classified according to the functions of the circuits in which they are used. This classification includes rectifier diodes, negative-resistance diodes, constant-voltage diodes, light-sensitive diodes, light-emitting diodes, capacitor diodes, and diode lasers.
Industry:Science
A two-terminal electronic device that utilizes the properties of the semiconductor from which it is constructed. In a semiconductor diode without a <i>pn</i> junction, the bulk properties of the semiconductor itself are used to make a device whose characteristics may be sensitive to light, temperature, or electric field. In a diode with a <i>pn</i> junction, the properties of the <i>pn</i> junction are used. The most important property of a <i>pn</i> junction is that, under ordinary conditions, it will allow electric current to flow in only one direction. Under the proper circumstances, however, a <i>pn</i> junction may also be used as a voltage-variable capacitance, a switch, a light source, a voltage regulator, or a means to convert light into electrical power.
Industry:Science
A two-terminal semiconductor junction device (also called the Esaki diode) which does not show rectification in the usual sense, but exhibits a negative resistance region at very low voltage in the forward-bias characteristic and a short circuit in the negative-bias direction.
Industry:Science
A two-terminal semiconductor junction device with a very sharp voltage breakdown as reverse bias is applied. The device is used to provide a voltage reference. It is named after C. Zener, who first proposed electronic tunneling as a mechanism of electrical breakdown in insulators.
Industry:Science
