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  • 1
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    Collision and annihilation of relative equilibrium points around asteroids with a changing parameter (2015)
    Oxford University Press
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    Publication Date: 2015-08-09
    Description: In this work, we investigate the bifurcations of relative equilibria in the gravitational potential of asteroids. A theorem concerning a conserved quantity, which is about the eigenvalues and number of relative equilibria, is presented and proved. The conserved quantity can restrict the number of non-degenerate equilibria in the gravitational potential of an asteroid. It is concluded that the number of non-degenerate equilibria in the gravitational field of an asteroid varies in pairs and is an odd number. In addition, the conserved quantity can also restrict the kinds of bifurcations of relative equilibria in the gravitational potential of an asteroid when the parameter varies. Furthermore, studies have shown that there exist transcritical bifurcations, quasi-transcritical bifurcations, saddle–node bifurcations, saddle–saddle bifurcations, binary saddle–node bifurcations, supercritical pitchfork bifurcations, and subcritical pitchfork bifurcations for the relative equilibria in the gravitational potential of asteroids. It is found that for the asteroid 216 Kleopatra, when the rotation period varies as a parameter, the number of relative equilibria changes from 7 to 5 to 3 to 1, and the bifurcations for the relative equilibria are saddle–node bifurcations and saddle–saddle bifurcations.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Tektites and the age paradox in mid-pleistocene china (2007)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2007-09-11
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Koeberl, C -- Glass, B P -- Keates, S G -- Potts, R -- Weiwen, H -- Yamei, H -- Deino, A -- Baoyin, Y -- Zhengtang, G -- Clark, J -- New York, N.Y. -- Science. 2000 Jul 28;289(5479):507a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17832054" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Mid-Pleistocene Acheulean-like stone technology of the Bose basin, South China (2000)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2000-03-04
    Description: Stone artifacts from the Bose basin, South China, are associated with tektites dated to 803,000 +/- 3000 years ago and represent the oldest known large cutting tools (LCTs) in East Asia. Bose toolmaking is compatible with Mode 2 (Acheulean) technologies in Africa in its targeted manufacture and biased spatial distribution of LCTs, large-scale flaking, and high flake scar counts. Acheulean-like tools in the mid-Pleistocene of South China imply that Mode 2 technical advances were manifested in East Asia contemporaneously with handaxe technology in Africa and western Eurasia. Bose lithic technology is associated with a tektite airfall and forest burning.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yamei, H -- Potts, R -- Baoyin, Y -- Zhengtang, G -- Deino, A -- Wei, W -- Clark, J -- Guangmao, X -- Weiwen, H -- New York, N.Y. -- Science. 2000 Mar 3;287(5458):1622-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Box 643, Beijing 100044, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10698732" target="_blank"〉PubMed〈/a〉
    Keywords: Africa ; Animals ; *Anthropology ; Archaeology ; China ; History, Ancient ; *Hominidae ; Humans
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Constructing the natural families of periodic orbits near irregular bodies (2015)
    Oxford University Press
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    Publication Date: 2015-09-06
    Description: The periodic orbits in the potential of an irregular body have proved to be of various morphologies and distributed widely over a large scale. This study is motivated by finding a construction that organizes the periodic motion set in a natural way, which would contribute to our understanding of the orbital dynamics in the near-field regime of the minor planets in the Solar system. An analysis of the first-order local continuation condition presents the feasible solution set, which essentially depends on the eigen subspace of the monodromy affiliated with the trivial multiplier +1. We introduce a base category due to the algebraic multiplicity of multiplier +1 of any periodic orbit, m a , and then look at the details of the correlations between the uniqueness of the local continuation and the multiplicities of +1. A specific application of the periodic orbits around asteroid (243) Ida is shown as a demonstration. The data base of periodic orbits around Ida is established, based on which we performed numeric continuations and confirmed the existence of eight topological types of the double case ( m a  = 2) as well as two of the quadruple case ( m a  = 4). The local analysis outlines, in general, how a complete natural family is constructed in phase space. Sample natural families are presented, with special attention paid to the topological transitions. An analysis reveals several common features among these topological transitions, and we take these features as a sketch of an arbitrary natural family of periodic orbits, which serves as a bridge to understanding the general orbital behaviours near irregular bodies.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Preliminary discussion on the origin of Lei-gong-mo (tektites) (1983)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: The specimens of lei-gong-mo (tektites) were collected from Hainan Island and Leizhow Peninsula during the period from 1963 to 1975. The distribution, forms, sculpture, abration surface (bald spot), internal structure and chemical composition of lei-gong-mo are discussed. Studies of these materials lead to the following conclusions: (1) the specimens of lei-gong-mo can be morphologically divided into eight types; (2) the sculptures on the surface of lei-gong-mo are probably due to the corrosion effect of volcanic gas, and the abration surface due to the aerodynamic corrosion; (3) the folded structures in the layered lei-gong-mo (Muong Nong-type tektite) seem hardly to be formed by an impact of meteorites, but they might be produced in the magma flow process when the lei-gong-mo was melting within the crater vent; and (4) the comparison of its chemical composition with that of basalt from Hainan Island does not show that lei-gong-mo came from the local volcano. The hypothesis of the lunar volcanic origin of tektites is examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-77328 , NAS 1.15:77328
    Format: application/pdf
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