摘要:

We now believe that only the lightest elements, hydrogen and helium, were created during the ‘Big Bang’ origin of the Universe and that all heavier elements were synthesized by nuclear reactions in stars, the interstellar medium and possibly in ‘little bangs’ in the nuclei of galaxies. The composition of the interstellar medium has evolved through enrichment by processed material shed by evolving stars and the composition of the Solar System reflects that of the interstellar medium at the time of its formation. Differentiation processes during the evolution of the Solar System and individual planets account for the different compositions of the Sun and planets. The measurement of the abundance distribution of the elements has become a very powerful tool in the elucidation of the evolution of the Solar System, stars and the Galaxy. This review attempts to trace the formation of the elements in stars and their subsequent evolution.

ISSN:0010-7514    

DOI:10.1080/00107517808210865

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

In this paper the principles of operation of various types of solar cell are described. Progress in photovoltaics is traced through the development of the monocrystalline silicon cell for space applications where the emphasis is upon reliability and power/weight ratio, to terrestrial cells where the emphasis is upon low-cost production. The role of other contenders such as polycrystalline silicon, amorphous silicon and cuprous sulphide/cadmium sulphide is discussed. Both silicon and gallium arsenide cells may be operated in conjunction with optical concentrators and sun-tracking equipment. This approach is compared with the usual flat array approach. The various national programmes for developing photovoltaic power sources are described, and the cost and production goals laid down in the American programme are quoted. Photovoltaic power sources are capital intensive, but once installed are cheap to operate and maintain, and in this respect they differ from conventional power sources. The economic viability of photovoltaic power sources depends critically upon the magnitude of real interest rates, and we show that when inflation is taken into account, photovoltaic power sources are competitive in many situations.

ISSN:0010-7514    

DOI:10.1080/00107517808210866

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The faintness of the light received from distant stars, and the long periods of exposure needed in astronomy to attain optimum density in the recorded image, bring to prominence two shortcomings in plates as they arrive from the manufacturer. One is very low quantum efficiency—less than one per cent—in which far too many photons are lost in unproductive events, the other is reciprocity failure in which the optical density of the developed image is not linearly related to the apparent brightness of the object. Post-manufacturing processes, known as hypersensitization, are applied in the observatories to increase plate speed and quantum efficiency and to reduce or eliminate reciprocity failure. Such techniques have revitalized the continued use of the older types of plate and are essential for the application of the new, fine-grain materials which have higher resolving power, but barely acceptable speed before treatment.

ISSN:0010-7514    

DOI:10.1080/00107517808210867

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Because of the long-range behaviour of the internuclear potential representing the interaction between two atoms (e.g. —C6R−6), there are usually a certain number of closely spaced vibrational-rotational levels that approach dissociation. The properties of molecules in these highest levels are quite unusual (although often simply related to the long-range forces), and we shall refer to such molecules by a special classification: ‘long-range molecules’. Restricting our attention todiatomiclong-range molecules, we first review the general relationship between the potential energy curve and vibrational levels. The long-range portion of potential energy curves is examined in detail and the simple properties of vibrational levels sensitive to these long-range potentials discussed. Finally transitions (radiative, nonradiative, and collision-induced) are briefly described.

ISSN:0010-7514    

DOI:10.1080/00107517808210868

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107517808210869

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107517808210870

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107517808210871

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Diatomic Molecules: a Critical Bibliography of Spectroscopic Data(Volume II). Established by R. F. Barrow. (CNRS, 1975.) [Pp. 194-386.] Scope: Survey; library (reference). Level: For specialists only.

ISSN:0010-7514    

DOI:10.1080/00107517808210872

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

ISSN:0010-7514    

DOI:10.1080/00107517808210873

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor