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Eiichiro Kokubo Keiko Yoshinaga & Junichiro Makino 《Monthly notices of the Royal Astronomical Society》1998,297(4):1067-1072
We describe a P(EC) n Hermite scheme for planetary N -body simulation. The fourth-order implicit Hermite scheme is a time-symmetric integrator that has no secular energy error for the integration of periodic orbits with time-symmetric time-steps. In general N -body problems, however, this advantage is of little practical significance, since it is difficult to achieve time-symmetry with individual variable time-steps. However, we can easily enjoy the benefit of the time-symmetric Hermite integrator in planetary N -body systems, where all bodies spend most of the time on nearly circular orbits. These orbits are integrated with almost constant time-steps even if we adopt the individual time-step scheme. The P(EC) n Hermite scheme and almost constant time-steps reduce the integration error greatly. For example, the energy error of the P(EC)2 Hermite scheme is two orders of magnitude smaller than that of the standard PEC Hermite scheme in the case of an N = 100, m = 1025 g planetesimal system with the rms eccentricity 〈 e 2 〉1/2 ≲0.03. 相似文献
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The long-lived nuclide 92Nb together with 91Nb and 94Nb were produced from Mo by neutron irradiation. The activities of the nuclides were determined by γ spectroscopy and the atomic abundances were determined by mass spectrometry. Intercomparison of 92Nb and 94Nb activities and abundances yielded a value for half-life yr based on a value for half-life yr. The same value was obtained within errors from absolute counting data and dilution analysis. 相似文献
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Fumiyoshi Makino 《Astrophysics and Space Science》1975,37(1):115-130
Balloon observations of the cosmic diffuse component of hard X-rays were conducted with two independent directional counters in two energy bands, from 20 keV to 120 keV and from 90 keV to 4 MeV. The build-up effect of primary X-rays and the altitude dependence of atmospheric X-rays were properly taken into account in the analysis of the growth curves. These two experiments gave consistent results in the overlapping energy region. If the differential energy spectrum of the photon flux is represented by a power lawE ?α, the value of α is 2.3 up to 100 keV, gradually increases to 2.8 at about 500 keV, and decreases to 2.0 thereabove. The spectrum above 300 keV is in parallel to the Apollo-15 spectrum, whereas the absolute intensity is somewhat smaller. The shape of the spectrum suggests the necessity of a multi-component theory on the origin of cosmic diffuse X-rays. 相似文献
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Many problems in galactic dynamics require computer speeds orders of magnitude larger than what can be achieved on current single-processor machines. In the near future such speeds are likely to become available through computer architectures based on large-scale, fine-grained parallelism. An example of a highly parallel computer is the Connection Machine, with up to 65,636 processors. We have benchmarked gravitationalN-body algorithms on the Connection Machine, and compared those with similar benchmarks which we have obtained on more traditional vector supercomputers. Our conclusions are: (1) The direct summation algorithm, with of orderN
2 interactions forN particles, can be made to run with high efficiency on either type of computer. As a result, the Connection Machine clearly wins in speed over all supercomuters tested, with the exception of an 8-processor ETA, which shows a comparable performance. (2) A more efficient tree algorithm reduces the growth of the number of interactions fromN
2 toN logN. However, the greater complexity of this algorithm causes a considerable degradation of efficiency, by a factor which is larger on the Connection Machine than on vector supercomputers. As a result, out tree code runs at comparable speeds on both types of machines, with the notable exception of the 8-processor ETA, which has an extrapolated speed for running our tree code which is higher than any of the other machines we have tested. 相似文献
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Positioning fisheries in a changing world 总被引：1，自引：1，他引：0
R. Quentin Grafton Ray Hilborn Lori Ridgeway Dale Squires Meryl Williams Serge Garcia Theodore Groves James Joseph Kieran Kelleher Tom Kompas Gary Libecap Carl Gustaf Lundin Mitsutaku Makino Thorolfur Matthiasson Richard McLoughlin Ana Parma Gustavo San Martin Ben Satia Carl-Christian Schmidt Maree Tait Lin Xiu Zhang 《Marine Policy》2008,32(4):630-634
Marine capture fisheries face major and complex challenges: habitat degradation, poor economic returns, social hardships from depleted stocks, illegal fishing, and climate change, among others. The key factors that prevent the transition to sustainable fisheries are information failures, transition costs, use and non-use conflicts and capacity constraints. Using the experiences of fisheries successes and failures it is argued only through better governance and institutional change that encompasses the public good of the oceans (biodiversity, ecosystem integrity, sustainability) and societal values (existence, aesthetic and amenity) will fisheries be made sustainable. 相似文献
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R. Armellin P. Di Lizia M. Berz K. Makino 《Celestial Mechanics and Dynamical Astronomy》2010,107(3):377-395
A novel method to compute all critical points of the distance function between two Keplerian orbits (either bounded or unbounded)
with a common focus is presented. The problem is attacked as a global optimization problem, solved by a rigorous global optimizer
based on Taylor models. Thus, thigh enclosures of the stationary points are obtained. The embedded capability of the method
of delivering high-order Taylor expansions is then used to analyze how uncertain orbital parameters affect the position of
the stationary points and the associated distance values. Sample orbital sets and Apophis asteroid are used as test cases. 相似文献
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M. Matsuoka M. Fujii S. Miyamoto J. Nishimura M. Oda Y. Ogawara S. Hayakawa I. Kasahara F. Makino Y. Tanaka P. C. Agrawal B. V. Sreekantan 《Astrophysics and Space Science》1972,18(2):472-490
Simultaneous hard X-ray and optical observations of Sco X-1 were carried out on 1971 May 1 at Hyderabad, India, when Sco X-1 was optically bright. The X-ray intensity observed by balloon-borne counter telescopes increased in coincidence with optical enhancements, while the plasma temperature derived by fitting the X-ray spectrum in the energy range 20–40 keV to the thermal bremsstrahlung spectrum did not appreciably change over the whole period of observation. 相似文献