F. G. Eparvier  P. C. Chamberlin  T. N. Woods  E. M. B. Thiemann 《Space Science Reviews》2015,195(1-4):293-301

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A. V. Shchukin  A. V. Il’inkov  N. F. Maksimov 《Russian Aeronautics (Iz VUZ)》2010,53(1):95-101

In this paper, the results of an experimental study concerning average heat transfer in an annular channel with flow swirling by an endless screw and spherical grooves on the convex surface are presented. Also analyzed is the heat and hydraulic efficiency of grooves application under conditions being considered.  相似文献   

    

M. F. El Eid  L.-S. The  B. S. Meyer 《Space Science Reviews》2009,147(1-2):1-29

We present a general overview of the structure and evolution of massive stars of masses ≥12 M _⊙ during their pre-supernova stages. We think it is worth reviewing this topic owing to the crucial role of massive stars in astrophysics, especially in the evolution of galaxies and the universe. We have performed several test computations with the aim to analyze and discuss many physical uncertainties still encountered in massive-star evolution. In particular, we explore the effects of mass loss, convection, rotation, ¹²C(α,γ)¹⁶O reaction and initial metallicity. We also compare and analyze the similarities and differences among various works and ours. Finally, we present useful comments on the nucleosynthesis from massive stars concerning the s-process and the yields for ²⁶Al and ⁶⁰Fe.  相似文献   

    

Lauretta  D. S.  Balram-Knutson  S. S.  Beshore  E.  Boynton  W. V.  Drouet d’Aubigny  C.  DellaGiustina  D. N.  Enos  H. L.  Golish  D. R.  Hergenrother  C. W.  Howell  E. S.  Bennett  C. A.  Morton  E. T.  Nolan  M. C.  Rizk  B.  Roper  H. L.  Bartels  A. E.  Bos  B. J.  Dworkin  J. P.  Highsmith  D. E.  Lorenz  D. A.  Lim  L. F.  Mink  R.  Moreau  M. C.  Nuth  J. A.  Reuter  D. C.  Simon  A. A.  Bierhaus  E. B.  Bryan  B. H.  Ballouz  R.  Barnouin  O. S.  Binzel  R. P.  Bottke  W. F.  Hamilton  V. E.  Walsh  K. J.  Chesley  S. R.  Christensen  P. R.  Clark  B. E.  Connolly  H. C.  Crombie  M. K.  Daly  M. G.  Emery  J. P.  McCoy  T. J.  McMahon  J. W.  Scheeres  D. J.  Messenger  S.  Nakamura-Messenger  K.  Righter  K.  Sandford  S. A. 《Space Science Reviews》2017,212(1-2):925-984

In May of 2011, NASA selected the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission as the third mission in the New Frontiers program. The other two New Frontiers missions are New Horizons, which explored Pluto during a flyby in July 2015 and is on its way for a flyby of Kuiper Belt object 2014 MU69 on January 1, 2019, and Juno, an orbiting mission that is studying the origin, evolution, and internal structure of Jupiter. The spacecraft departed for near-Earth asteroid (101955) Bennu aboard an United Launch Alliance Atlas V 411 evolved expendable launch vehicle at 7:05 p.m. EDT on September 8, 2016, on a seven-year journey to return samples from Bennu. The spacecraft is on an outbound-cruise trajectory that will result in a rendezvous with Bennu in November 2018. The science instruments on the spacecraft will survey Bennu to measure its physical, geological, and chemical properties, and the team will use these data to select a site on the surface to collect at least 60 g of asteroid regolith. The team will also analyze the remote-sensing data to perform a detailed study of the sample site for context, assess Bennu’s resource potential, refine estimates of its impact probability with Earth, and provide ground-truth data for the extensive astronomical data set collected on this asteroid. The spacecraft will leave Bennu in 2021 and return the sample to the Utah Test and Training Range (UTTR) on September 24, 2023.

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Grasset  O.  Castillo-Rogez  J.  Guillot  T.  Fletcher  L. N.  Tosi  F. 《Space Science Reviews》2017,212(1-2):835-875

Space Science Reviews - Space exploration and ground-based observations have provided outstanding evidence of the diversity and the complexity of the outer solar system. This work presents our...  相似文献   

    

F.G.CANALES  J.L.MANTARI 《中国航空学报》2017,30(5)

This paper presents an analytical solution for static analysis of thick rectangular beams with different boundary conditions.Carrera's Unified Formulation (CUF) is used in order to consider shear deformation theories of arbitrary order.The novelty of the present work is that a boundary discontinuous Fourier approach is used to consider clamped boundary conditions in the analytical solution,unlike Navier-type solutions which are restricted to simply supported beams.Governing equations are obtained by employing the principle of virtual work.The numerical accuracy of results is ascertained by studying the convergence of the solution and comparing the results to those of a 3D finite element solution.Beams subjected to bending due to a uniform pressure load and subjected to torsion due to opposite linear forces are considered.Overall,accurate results close to those of 3D finite element solutions are obtained,which can be used to validate finite element results or other approximate methods.  相似文献   

  总被引：1，自引：0，他引：1  

Robert F. Pfaff Jr. 《Space Science Reviews》2012,168(1-4):23-112

An overview of the plasma environment near the earth is provided. We describe how the near-earth plasma is formed, including photo-ionization from solar photons and impact ionization at high latitudes from energetic particles. We review the fundamental characteristics of the earth’s plasma environment, with emphasis on the ionosphere and its interactions with the extended neutral atmosphere. Important processes that control ionospheric physics at low, middle, and high latitudes are discussed. The general dynamics and morphology of the ionized gas at mid- and low-latitudes are described including electrodynamic contributions from wind-driven dynamos, tides, and planetary-scale waves. The unique properties of the near-earth plasma and its associated currents at high latitudes are shown to depend on precipitating auroral charged particles and strong electric fields which map earthward from the magnetosphere. The upper atmosphere is shown to have profound effects on the transfer of energy and momentum between the high-latitude plasma and the neutral constituents. The article concludes with a discussion of how the near-earth plasma responds to magnetic storms associated with solar disturbances.  相似文献   

    

Primas  F. 《Space Science Reviews》1998,84(1-2):161-166

The boron 2500 spectral region has been observed with the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) in a new set of metal-poor stars and analyzed by spectrum synthesis technique, adopting the most recent model atmospheres. By taking into account the Li and Be abundances available from the literature for this same set of objects, the resulting patterns of their light elements abundances cannot be easily justified with the currently known stellar structure scenarios. The finding of real differences in the B content between stars with very similar stellar characteristics suggest that also production effects, rather than depletion and/or mixing only, should be taken into account as a possible and valuable explanation.  相似文献   

    

Spite  F.  Spite  M.  Hill  V. 《Space Science Reviews》1998,84(1-2):155-160

The relation between the lithium abundance observed in Population II stars and the primordial abundance, is still an open question (see Cayrel and Duncan, this meeting). A few recent results are discussed. HIPPARCOS data show that the standard model of stellar evolution can explain the 6Li detection in HD 84937, suggesting a negligible depletion of 7Li. A slope in the Li/Teff relation for Pop II dwarfs and a spread of their Li abundance have been advocated, and both used as arguments in favor of Li depletion. The slope is not confirmed when two other independent temperature scales are used. The Li scatter around the plateau is hardly larger than the scatter predicted from determination errors. Hints from a scatter of Li in subgiants of the globular cluster M92 are not completely conclusive. The determination of more accurate Li abundances in the Pop II stars is an urgent but difficult task, requiring better model atmosphere (better convection treatment) and the help of observational data about Pop II stars (such as long base interferometry).  相似文献   

  总被引：1，自引：0，他引：1  

Reinisch  B.W.  Haines  D.M.  Bibl  K.  Cheney  G.  Galkin  I.A.  Huang  X.  Myers  S.H.  Sales  G.S.  Benson  R.F.  Fung  S.F.  Green  J.L.  Boardsen  S.  Taylor  W.W.L.  Bougeret  J.-L.  Manning  R.  Meyer-Vernet  N.  Moncuquet  M.  Carpenter  D.L.  Gallagher  D.L.  Reiff  P. 《Space Science Reviews》2000,91(1-2):319-359

Radio plasma imaging uses total reflection of electromagnetic waves from plasmas whose plasma frequencies equal the radio sounding frequency and whose electron density gradients are parallel to the wave normals. The Radio Plasma Imager (RPI) has two orthogonal 500-m long dipole antennas in the spin plane for near omni-directional transmission. The third antenna is a 20-m dipole along the spin axis. Echoes from the magnetopause, plasmasphere and cusp will be received with the three orthogonal antennas, allowing the determination of their angle-of-arrival. Thus it will be possible to create image fragments of the reflecting density structures. The instrument can execute a large variety of programmable measuring options at frequencies between 3 kHz and 3 MHz. Tuning of the transmit antennas provides optimum power transfer from the 10 W transmitter to the antennas. The instrument can operate in three active sounding modes: (1) remote sounding to probe magnetospheric boundaries, (2) local (relaxation) sounding to probe the local plasma frequency and scalar magnetic field, and (3) whistler stimulation sounding. In addition, there is a passive mode to record natural emissions, and to determine the local electron density, the scalar magnetic field, and temperature by using a thermal noise spectroscopy technique.  相似文献