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31.
Gijs de Vries 《Space Policy》1987,3(4):288-292
European Community action on broadcasting standards is desperately needed. This article examines the issue of technical standards, by looking first at the MAC packets directive on European standards for DBA transmission. It then considers high-definition television and the search for global standards. The author concludes by drawing some lessons regarding the European Community's involvement in high technology, and its role in broadcasting in particular. 相似文献
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We review the implications of modern higher-dimensional theories of gravity for astrophysics and cosmology. In particular, we discuss the latest developments of STM theory in connection with dark matter, particle dynamics and the cosmological constant, as well as related aspects of quantum theory. There are also more immediate tests of extra dimensions, notably involving perturbations of the cosmic 3K microwave background and the precession of a supercooled gyroscope in Earth orbit. We also outline some general features of embeddings, and include pictures of the big bang as viewed from a higher dimension. 相似文献
34.
The complex system of linear features on Phobos—the inner moon of Mars—found by the Viking Orbiters in 1976, can be classified morphologically into three types according to their appearance as well as their geometrical distribution on the surface. One kind of grooves appears to form arcs of small circles normal to the Phobos-Mars direction. We propose that these grooves are the surface manifestation of layering within Phobos[4–6] which could have been formed when Phobos was a part of a much larger and geologically active parent planet.Here we suggest some measurements to observe whether Phobos has a layered structure or not. The suggestion contains remote sensing measurements (particularly determination of the magnetic field by magnetometer and by electron reflection method) by a spacecraft orbiting around Mars as well as surface measurements (active seismic reflection experiment) by a landing module on Phobos. 相似文献
35.
C. de Jager A. Ollongren Tj. de Graaf B. J. Levin M. Tucker 《Space Science Reviews》1969,9(5):740-742
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As we resolve ever smaller structures in the solar atmosphere, it has become clear that magnetism is an important component of those small structures. Small-scale magnetism holds the key to many poorly understood facets of solar magnetism on all scales, such as the existence of a local dynamo, chromospheric heating, and flux emergence, to name a few. Here, we review our knowledge of small-scale photospheric fields, with particular emphasis on quiet-sun field, and discuss the implications of several results obtained recently using new instruments, as well as future prospects in this field of research. 相似文献
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Gy Rontó A Bérces A Fekete G Kovács P Gróf H Lammer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(8):1302-1305
Polycrystalline uracil thin layers participate in the phage and uracil response (PUR) experiment, assigned to the biological dosimetry of the extraterrestrial solar radiation on the International Space Station (ISS). In ground based experiments (experiment verification tests), the following space parameters were simulated and studied: temperature, vacuum and short wavelength UV (UV-C, down to 200 nm) radiation. The closed uracil samples proved to be vacuum-tight for 7 days. In the tested temperature range (from -20 to +40 degrees C) the uracil samples are stable. The kinetic of dimer formation (dimerization) and reversion (monomerization) of uracil dimers due to short wavelength UV radiation was detected, the monomerization efficiency of the polychromatic deuterium lamp is higher than that of the germicidal lamp. A mathematical model describing the kinetic of monomerization-dimerization was constructed. Under the influence of UV radiation the dimerization-monomerization reactions occur simultaneously, thus the additivity law of the effect of the various wavelengths is not applicable. 相似文献
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