- 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 rigid body mounted on a fixed horizontal axis, about which it is free to rotate under the influence of gravity. The period of the motion of a pendulum is virtually independent of its amplitude and depends primarily on the geometry of the pendulum and on the local value of <i>g</i>, the acceleration of gravity. Pendulums have therefore been used as the control elements in clocks, or inversely as instruments to measure <i>g</i>.
Industry:Science
A rigid material whose structure lacks crystalline periodicity; that is, the pattern of its constituent atoms or molecules does not repeat periodically in three dimensions. In the present terminology amorphous and noncrystalline are synonymous. A solid is distinguished from its other amorphous counterparts (liquids and gases) by its viscosity: a material is considered solid (rigid) if its shear viscosity exceeds 10<sup>14.6</sup> poise (10<sup>13.6</sup> pascal · second).
Industry:Science
A rock composed of 90 vol % or more of plagioclase feldspar. Strictly, the rock is composed entirely of crystals discernible with the eye, but some finely crystalline examples from the Moon have been called anorthosite or anorthositic breccia. Two principal types of anorthosite are based on field occurrence: layers in stratified complexes of igneous rock, and large massifs of rock up to 12,000 mi<sup>2</sup> (30,000 km<sup>2</sup>) in area. Scientists have been fascinated with anorthosites because they are spectacular rocks (dark varieties are quarried and polished for ornamental use); valuable deposits of iron and titanium ore are associated with anorthosites; and the massif anorthosites appear to have been produced during a unique episode of ancient Earth history (about 1–2 billion years ago).
Industry:Science
A rock consisting of more than 90% of millimeter-to-centimeter-sized crystals of olivine, pyroxene, and hornblende, with more than 40% olivine. Other minerals are mainly plagioclase, chromite, and garnet. Much of the volume of the Earth's mantle probably is peridotite.
Industry:Science
A rock fragment enclosed in another rock, and of varying degrees of foreigness. Cognate xenoliths, for example, are pieces of rock that are genetically related to the host rock that contains them, such as pieces of a border zone in the interior of the same body. Included blocks of unrelated rocks are more deserving of the xenolith label. Such foreign rocks help establish the once fluid and hence molten condition of invading magma capable of incorporating and mixing an assemblage of unrelated rock inclusions, as at Hutton's Rock near Edinburgh, Scotland. Dark inclusions, commony called enclaves, up to many feet in length can be found in granitic plutons and silicic lava domes and flows. In many cases, these have fine-grained borders against the enclosing rock and are interpreted to be lenses of formerly fluid basaltic magma which crystallized as a result of contact with cooler surrounding silicic magma.
Industry:Science
A rock froth, formed by the extreme puffing up (vesiculation) of liquid lava by expanding gases liberated from solution in the lava prior to and during solidification. Some varieties will float in water for many weeks before becoming waterlogged. Typical pumice is siliceous (rhyolite or dacite) in composition, but the lightest and most vesicular pumice (known also as reticulite and thread-lace scoria) is of basaltic composition.
Industry:Science
A rock mainly comprising minerals that are hydrous aluminum oxides. These minerals are gibbsite, boehmite, and diaspore. The major impurities in bauxite are clay minerals and iron oxides. Bauxite is a weathering product of aluminous rock that results from intense leaching in tropical and subtropical areas, a process called laterization. Bauxite deposits are generally found on plateaus in stable areas where they had sufficient geologic time to form and were protected from erosion.
Industry:Science
A rock that has undergone significant modification of original textures by predominantly plastic flow due to dynamic recrystallization. Mylonites form at depth beneath brittle faults in continental and oceanic crust, in rocks from quartzo-feldspathic to olivine-pyroxenite composition. Mylonites were once confused with cataclasites, which form by brittle fracturing, crushing, and comminution. Microstructures that develop during mylonitization vary according to original mineralogy and modal compositions, temperature, confining pressure, strain, strain rate, applied stresses, and presence or absence of fluids.
Industry:Science
A rod or bar, usually circular in cross section, used in structural parts of machines to tie together or brace connected members, or, in moving parts of machines or mechanisms, used to connect arms or parts to transmit motion. In the first use the rod ends are usually a threaded fastening, while in the latter they are usually forged into an eye for a pin connection.
Industry:Science
A rodent in the family Sciuridae. This family includes all tree squirrels and flying squirrels, as well as squirrels that live on the ground such as the woodchuck, marmot, chipmunk, and prairie dog. There are 51 living genera and 272 species living in a wide variety of habitats ranging through tropical rainforests, tundra, alpine meadows, and semiarid deserts in Europe, Asia, Africa, North America, and most of South Africa. They are absent from Australia, Madagascar, Polynesia, and the Sahara Desert. Locomotion is plantigrade (walking with the whole sole of the foot touching the ground). Sensitive vibrissae are present on the head, feet, and outsides of the legs. The dental formula is I 1/1, C 0/0, Pm 1-2/1, M 3/3 for a total of 20 or 22 teeth. The incisors grow continually throughout the animal's life.
Industry:Science
