Książki na temat „One-Dimensional gas”

In this chapter gas flow through pipes is analysed, taking account of compressibility and either friction or heat exchange with the fluid. It is shown that in all cases the key parameter is the Mach number. The analyses are based upon the conservation laws for mass, momentum, and energy, together with an equation of state. So that significant results can be achieved, the flowing fluid is treated as a perfect gas, and the flow as one dimensional. Adiabatic pipe flow with wall friction is termed Fanno flow. Frictionless pipe flow with heat transfer is termed Rayleigh flow. It is found that both flows, and also isothermal pipe flow with wall friction, can be limited by choking.

Compressible-gas flow through convergent and convergent-divergent nozzles is analysed in this chapter based upon the conservation laws for mass, momentum, and energy, together with considerations of thermodynamics. It is shown that in both cases the key parameter in describing the flow is the Mach number, which is used to distinguish between subsonic and supersonic flow. So that significant results can be achieved, the flowing fluid is treated as a perfect gas, and the flow as one dimensional. Flow through a convergent nozzle and the choking limitation is discussed. Flow through a normal shockwave, which is an important feature of supersonic flow, is also analysed. No account is taken of surface friction or heat transfer, and the flow upstream and downstream of a shockwave is treated as isentropic. In addition, the conditions are discussed under which a shockwave arises in compressible flow through a convergent-divergent nozzle.

Unambiguous and homogeneous geodetic reference frames are essential to the proper determination of locations and heights. The reference frames used in the Netherlands are the Rijksdriehoekmeting (RD) for locations and the Normaal Amsterdamse Peil (NAP) for heights. The RD has traditionally been managed by the Kadaster; the NAP by Rijkswaterstaat. The emergence of satellite positioning has resulted in drastic changes to these geodetic reference frames. A surveyor is now offered one instrument, GPS (the Global Positioning System), capable of the simultaneous determination of locations and heights. This is possible by virtue of one three-dimensional geodetic reference system - the European Terrestrial Reference System (ETRS89) - which in the Netherlands is maintained in a collaborative arrangement between the Kadaster and Rijkswaterstaat. GPS has been advanced as a practical measurement technique by linking the definition of the RD grid to ETRS89. Nevertheless the introduction of GPS also revealed distortions in the RD grid, which are modelled in the RDNAPTRANSTM2004 transformation. Furthermore, the use of the geoid model has become essential to the use of GPS in determining the height in comparison to NAP. Subsidence that has disrupted the backbone of the NAP gave cause to the need for a large-scale adjustment of the heights of the underground benchmarks and, in so doing, of the grid. Consequently new NAP heights have been introduced at the beginning of 2005; a new definition of the RD grid that had already been introduced in 2000 was once again modified in 2004. During the past few years two NCG subcommissions have devoted a great deal of time to these modifications. This publication lays down ETRS89, the RD and the NAP, together with their mutual relationships. In addition to reviewing the history of the reference frames and the manner in which they are maintained (including, for example, the use of AGRS.NL as the basis for the Dutch geometric infrastructure), the publication also discusses the status of the frames as at 1 January 2005. This encompasses the realisation of ETRS89 via AGRS.NL, the revision and new definition of the RD grid in 2004, and the new NAP publication in 2005. The publication also describes the mutual relationships between the frames in the modernized RDNAPTRANSTM2004 transformation consisting of the new NLGEO2004 geoid model and a model for the distortions of the RD grid. In conclusion, the publication also devotes attention to the future maintenance of the ETRS89, RD and NAP. The continuity of the link between the traditional frames and the three-dimensional frames is of great importance, and ETRS89 will continue to fulfil this linking role. The GPS base network and AGRS.NL reference stations will increasingly assume the leading role in the maintenance of the RD frame. The maintenance of the NAP will continue to be necessary, although during the coming decades the the primary heights will not need revision. In so doing the high quality of the geodetic reference frames required for their use in actual practice will continue to be guaranteed.

Surfing the Quantum World bridges the gap between in-depth textbooks and typical popular science books on quantum ideas and phenomena. Among its significant features is the description of a host of mind-bending phenomena, such as a quantum object being in two places at once or a certain minus sign being the most consequential in the universe. Much of its first part is historical, starting with the ancient Greeks and their concepts of light, and ending with the creation of quantum mechanics. The second part begins by applying quantum mechanics and its probability nature to a pedagogical system, the one-dimensional box, an analog of which is a musical-instrument string. This is followed by a gentle introduction to the fundamental principles of quantum theory, whose core concepts and symbolic representations are the foundation for most of the subsequent chapters. For instance, it is shown how quantum theory explains the properties of the hydrogen atom and, via quantum spin and Pauli’s Exclusion Principle, how it accounts for the structure of the periodic table. White dwarf and neutron stars are seen to be gigantic quantum objects, while the maximum height of mountains is shown to have a quantum basis. Among the many other topics considered are a variety of interference phenomena, those that display the wave properties of particles like electrons and photons, and even of large molecules. The book concludes with a wide-ranging discussion of interpretational and philosophic issues, introduced in Chapters 14 by entanglement and 15 by Schrödinger’s cat.