- 行业: Printing & publishing
- Number of terms: 178089
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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.
The motion of a rigid body which takes place in such a way that all of its particles move in circles about an axis with a common angular velocity; also, the rotation of a particle about a fixed point in space. Rotational motion is illustrated by (1) the fixed speed of rotation of the Earth about its axis; (2) the varying speed of rotation of the flywheel of a sewing machine; (3) the rotation of a satellite about a planet, in which both the speed of rotation and the distance from the center of rotation may vary; (4) the motion of an ion in a cyclotron, where the angular speed of rotation remains constant, but the radius of the circular motion increases; and (5) the motion of a pendulum, in which case the particles describe harmonic motion along a circular arc.
Industry:Science
The prehistoric period when people made stone tools exclusively by chipping or flaking. John Lubbock proposed and defined the term Paleolithic, or Old Stone Age, in 1865, and also defined a subsequent stage, Neolithic or New Stone Age, during which some stone tools were formed by polishing or grinding. Later archeologists altered these definitions; to many today the Paleolithic is the period during which human beings lived entirely by hunting and gathering, while the Neolithic is the following interval during which plant and animal domestication was introduced. To other archeologists, the Paleolithic is simply a time interval, roughly equivalent to the Pleistocene Epoch, while the Neolithic comprises the early part of the succeeding Holocene (or Recent) Epoch.
Industry:Science
The principle that nature follows exact laws, so that what will happen in the future is a necessary consequence of the state of the world at any given moment in the past. This view, if fully adopted, implies that events which seem to occur by chance would be fully understood if more was known about them, and that apparently free thoughts and choices are explainable and in principle predictable in terms of neuroscience. In a looser sense, determinism refers to claims that mental freedom is much more restricted than is generally supposed. An immense philosophical literature has arisen in response to this challenge to the sense of humanity, most of it defending the freedom of a person's choices and the necessity that the individual be held responsible for them.
Industry:Science
The thymus gland is a primary lymphoid organ located in the neck or upper thorax of all vertebrates. It is a site of lymphocyte development. T-cell precursors (prothymocytes) migrate from the bone marrow to the thymus gland, where they undergo a stringent selection process. The microenvironment of the thymus is composed of nonlymphoid cells (epithelial cells, macrophages, dendritic cells, and fibroblasts) and extracellular matrix components. This environment stimulates the differentiation (maturation) of prothymocytes. The maturation includes the acquisition of T-cell function, leading to the mature and self-tolerant T cells that are found in the peripheral lymphoid organs. Classical hormones and neural innervation also affect lymphoid development and function.
Industry:Science
The solid angular luminous flux density in a given direction from a light source. It may be considered as the luminous flux on a small surface normal to the given direction, divided by the solid angle (in steradians) which the surface subtends at the source of light. Since the apex of a solid angle is a point, this concept applies exactly only to a point source. The size of the source, however, is often extremely small when compared with the distance from which it is observed, so in practice the luminous flux coming from such a source may be taken as coming from a point. For accuracy, the ratio of the diameter of the light source to the measuring distance should be about 1:10, although in practice ratios as large as 1:5 have been used without excessive error.
Industry:Science
The Solar TErrestrial RElations Observatory (STEREO) is a two-spacecraft NASA-led mission to study the three-dimensional structure of the Sun and heliosphere. STEREO's primary scientific objectives are to understand the mechanisms by which material leaves the Sun in both large eruptions called coronal mass ejections (CMEs) and the steady flow known as the solar wind, and to determine how this material propagates through the solar system. One of the two spacecraft that comprise the mission orbits the Sun ahead of the Earth, while the other trails the Earth. The separation between the two spacecraft allows them to capture stereoscopic images of the Sun and make in situ measurements that reveal the three-dimensional structure of interplanetary CMEs and the solar wind.
Industry:Science
The process of directing the movements of submersible vehicles, and divers, from one point to another. The development of improved submersible vehicles, coupled with advances in saturated diving, has resulted in new requirements for underwater navigation. Various methods which have proved successful include acoustic transponder systems, dead reckoning, surface-referenced navigation from a support ship, terrain map matching, homing, and various combinations of these. The choice of the navigation system depends on such factors as precision required, area to be covered, availability of surface vessels, sea state under which they are expected to operate, and the duration of the mission. Redundant systems are routinely provided to maintain the safety of crewed vehicles.
Industry:Science
The structure consisting of the wings, fuselage, and fin and tail plane (vertical and horizontal stabilizer) of an airplane. This structure has a clearly defined role: to resist all the extreme loads that can be experienced with no danger to the passengers, whether the aircraft be civil or military. The temptation therefore could be to overdesign the airframe and “play safe.” But an overweight civil aircraft would be commercially disastrous, and an overweight military aircraft could be outperformed. To put this matter into perspective, a civil airframe can be up to 40% of the total dry weight, whereas the payload may be as low as 20%. Thus a structure which is overdesigned by only 10% could reduce the payload by 20%. This represents the profit margin on many routes.
Industry:Science
The process of creating products, components, and structural systems with wood and wood-based materials. Wood engineering design applies concepts of engineering in the design of systems and products that must carry loads and perform in a safe and serviceable fashion. Common examples include structural systems such as buildings or electric power transmission structures, components such as trusses or prefabricated stressed-skin panels, and products such as furniture or pallets and containers. The design process considers the shape, size, physical and mechanical properties of the materials, type and size of the connections, and the type of system response needed to resist both stationary and moving (dynamic) loads, and function satisfactorily in the end-use environment.
Industry:Science
The study of gene structure and function in fungi. Genetic research has provided important knowledge about genes, heredity, genetic mechanisms, metabolism, physiology, and development in fungi, and in higher organisms in general, because in certain respects the fungal life cycle and cellular attributes are ideally suited to both mendelian and molecular genetic analysis. Fungal nuclei are predominantly haploid; that is, they contain only one set of chromosomes. This characteristic is useful in the study of mutations, which are usually recessive and therefore masked in diploid organisms. Mutational dissection is an important technique for the study of biological processes, and the use of haploid organisms conveniently allows for the immediate expression of mutant genes.
Industry:Science
