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221.
Space Science Reviews - 相似文献
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223.
Christoph Lotz Yvonne Wessarges Jörg Hermsdorf Wolfgang Ertmer Ludger Overmeyer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(8):1967-1974
Through the striving of humanity into space, new production processes and technologies for the use under microgravity will be essential in the future. Production of objects in space demands for new processes, like additive manufacturing. This paper presents the concept and the realization for a new machine to investigate microgravity production processes on earth. The machine is based on linear long stator drives and a vacuum chamber carrying up to 1000?kg. For the first time high repetition rate and associated low experimental costs can provide basic research. The paper also introduces the substrate-free additive manufacturing as a future research topic and one of our primary application. 相似文献
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225.
Thielemann F.-K. Hauser P. Kolbe E. Martinez-Pinedo G. Panov I. Rauscher T. Kratz K.-L. Pfeiffer B. Rosswog S. Liebendörfer M. Mezzacappa A. 《Space Science Reviews》2002,100(1-4):277-296
The age of the universe, measured from the Big Bang to the present, is at the focus of cosmology. Its determination relies, however, on the use of stellar objects or their products. Stellar explosions, like type Ia supernovae serve as standard(izable) candles to measure the expansion of the universe. Hertzsprung––Russell diagrams of globular clusters can determine the age of such clusters and thus are lower limits of the age of the galaxy and therefore also the universe. Some nuclear isotopes with half–lives comparable to the age of galaxies (and the universe) can serve as clocks (chronometers) for the duration of nucleosynthesis. The isotopes 238U and 232Th with half–lives of 4.5×109 and 1.4×1010 yr, decaying via alpha decay chains to Pb isotopes, are well suited to serve this purpose. They are products of the same nucleosynthesis process, the r-process. Therefore, the present paper aims at understanding the necessary environment conditions in the (stellar) production sites, the nuclear physics involved, the observational constraints for r-process nucleosynthesis, the results from nucleocosmochronology, and the remaining challenges and uncertainties which need to be overcome for a full understanding of the nature of the r-process. 相似文献
226.
Galaxy clusters are ideal tracers of the large-scale structure and evolution of the universe. They are thus good probes for the matter content of the universe, the existence of dark matter, and for the statistics of the large-scale structure of the matter distribution. X-ray observations provide a very effective tool to characterize individual galaxy clusters as well as the cluster population. With the detailed analysis of X-ray observations of galaxy clusters the matter composition of clusters is obtained which can be taken as representative of the matter composition of the universe. Based on galaxy cluster surveys in X-rays a census of the galaxy cluster population and statistical measures of the spatial distribution of clusters is obtained. Comparison of the results with predictions from cosmological models yields interesting cosmological model constraints and in particular favours a low density universe. 相似文献
227.
J.-P. Bibring H. Rosenbauer H. Boehnhardt S. Ulamec J. Biele S. Espinasse B. Feuerbacher P. Gaudon P. Hemmerich P. Kletzkine D. Moura R. Mugnuolo G. Nietner B. Pätz R. Roll H. Scheuerle K. Szegö K. Wittmann 《Space Science Reviews》2007,128(1-4):205-220
The paper describes the Rosetta Lander named Philae and introduces its complement of scientific instruments. Philae was launched
aboard the European Space Agency Rosetta spacecraft on 02 March 2004 and is expected to land and operate on the nucleus of
67P/Churyumov-Gerasimenko at a distance of about 3 AU from the Sun. Its overall mass is ~98 kg (plus the support systems remaining
on the Orbiter), including its scientific payload of ~27 kg. It will operate autonomously, using the Rosetta Orbiter as a
communication relay to Earth. The scientific goals of its experiments focus on elemental, isotopic, molecular and mineralogical
composition of the cometary material, the characterization of physical properties of the surface and subsurface material,
the large-scale structure and the magnetic and plasma environment of the nucleus. In particular, surface and sub-surface samples
will be acquired and sequentially analyzed by a suite of instruments. Measurements will be performed primarily during descent
and along the first five days following touch-down. Philae is designed to also operate on a long time-scale, to monitor the
evolution of the nucleus properties. Philae is a very integrated project at system, science and management levels, provided
by an international consortium. The Philae experiments have the potential of providing unique scientific outcomes, complementing
by in situ ground truth the Rosetta Orbiter investigations.
Philae team members are listed in the acknowledgements 相似文献
228.
The ionic charge of solar energetic particles (SEP) as observed in interplanetary space is an important parameter for the
diagnostic of the plasma conditions at the source region and provides fundamental information about the acceleration and propagation
processes at the Sun and in interplanetary space. In this paper we review the new measurements of ionic charge states with
advanced instrumentation onboard the SAMPEX, SOHO, and ACE spacecraft that provide for the first time ionic charge measurements
over the wide energy range of ∼0.01 to 70 MeV/nuc (for Fe), and for many individual SEP events. These new measurements show
a strong energy dependence of the mean ionic charge of heavy ions, most pronounced for iron, indicating that the previous
interpretation of the mean ionic charge being solely related to the ambient plasma temperature was too simplistic. This energy
dependence, in combination with models on acceleration, charge stripping, and solar and interplanetary propagation, provides
constraints for the temperature, density, and acceleration time scales in the acceleration region. The comparison of the measurements
with model calculations shows that for impulsive events with a large increase of Q
Fe(E) at energies ≤1 MeV/nuc the acceleration occurs low in the corona, typically at altitudes ≤0.2 R
S
. 相似文献
229.
N. Tarcea T. Frosch P. Rösch M. Hilchenbach T. Stuffler S. Hofer H. Thiele R. Hochleitner J. Popp 《Space Science Reviews》2008,135(1-4):281-292
This paper introduces Raman spectroscopy and discusses various scenarios where it might be applied to in situ planetary missions. We demonstrate the extensive capabilities of Raman spectroscopy for planetary investigations and argue that this technique is essential for future planetary missions. 相似文献