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221.
In computer simulations based on creeping motion equations, the difference in stress sensitivity of strain rate between Newtonian rheology and non-Newtonian power-law rheology does not greatly influence the types of mantled porphyroclast developed in simple shear viscous flows. Porphyroclast type is determined by the radius of an initial spherical mantle. When a thin mantle lies within the separatrix, (δ2-objects develop at small γ, then complex porphyroclasts appear with increasing γ. When the mantle is thicker and transected by the separatrix, φ-objects form at small γ and δ2-objects appear with increasing γ during the same deformation. The transition from φ- to δ2-objects is gradual, the transition strain being dependent on the initial radius of the mantle. Our simulations did not produce θ-, δ1- or σ-objects. 相似文献
222.
A three-dimensional formulation based on Green's functions of cylindrical loads in layered semi-infinite media is employed to investigate the dynamic behaviour of piles in homogeneous and non-homogeneous half spaces. The pile-soil-pile interaction taking place in pile groups is incorporated in the model. The results presented in this paper include the dynamic stiffnesses and dampings of single piles as well as those of representative 2 × 2 and 4 × 4 square pile groups in the soil media considered in this study. In addition, the distribution of forces applied on the pile cap among the individual piles in a group is investigated. 相似文献
223.
A. Masuda H. Shimizu S. Nakai A. Makishima S. Lahti 《Earth and Planetary Science Letters》1988,89(3-4)
LaCe ages are reported for two sets of Finnish pegmatites, Lövböle and Mustikkamäki, and for an Amiˆtsoq gneiss, Greenland. When λβ138La value (2.29 × 10−12 yr−1) obtained by radioactivity measurement [1] is used for the chronological calculation, the LaCe ages (2129, 2325, 3271 Myr) evaluated for these rocks are 18–35% older than the SmNd ages for the same samples. To make the LaCe age fit to the SmNd age for the same sample, a new value of (2.77 ± 0.21) × 10−12 yr−1 is evaluated for λβ138La. In this calculation, the LaCe and SmNd ages reported for a Bushveld gabbro [2] have been also taken into account together with those for the Lövböle pegmatite and the Mustikkamäki pegmatite, while the Amiˆtsoq gneiss (GGU110999) has been omitted because of the complicated thermal history of this sample. 相似文献
224.
Hidetaka Takeoka Yoshio Tanaka Yuichi Ohno Yukiharu Hisaki Akitsugu Nadai Hiroshi Kuroiwa 《Journal of Oceanography》1995,51(6):699-711
Observations of sea surface currents by HF radar were carried out in the Bungo Channel in summer 1992. The current ellipses of M2 constituent obtained by the observational results agree quite well with those obtained by the ADCP observations, showing that the accuracy of the HF radar measurements is of the same level as ADCP. The results revealed the current structures and their change with the Kyucho in detail. The Kyucho is influenced by the complicated coastal geometry and does not propagate straightly into the Bungo Channel. It propagates further inward after charging the coastal bays with warm water. The current directions change largely, since the currents turn around the stagnant region in the bay filled with the warm water. The northward intrusion begins to be weakened in the southern part of the channel, while it still persists in the northern part. The northward current speeds of the observed Kyucho are about 50 cm/s and sometimes attain 60 to 70 cm/s. 相似文献
225.
Hideo Miyake Seiji Sasaki Hidekazu Yamaguchi Kiyoshi Masuda Gen Anma Yoshihiko Kamei 《Journal of Oceanography》1995,51(1):99-109
Thermohaline staircases off Cape Erimo, Hokkaido are described and their physical properties are compared with those in other seas. The mean fluxes for heat and salt across the interface induced by salt finger were estimated as 105 cal cm–2d–1, and 0.03 g cm–2d–1, respectively. These values were in the same order as those in Caribbean Sea. The effective eddy diffusivities were also in the same order as the Caribbean ones. This suggests that the double-diffusive convection plays on important role on the water mass conversions occurring in the interfrontal zone between the Oyashio and the Kuroshio Waters. 相似文献
226.
Akihiko Ito Koki Ouchi Isamu Hisa Susumu Seki Yoshio Seto Shoji Kurashina 《Journal of Oceanography》1984,40(2):98-104
In the consideration of safety it is required that packages containing radioactive wastes when dumped at sea should keep their
integrity and retain their contents until they reach the seabed. Packages containing simulated radioactive wastes (non-radioactive)
were tested by a free-fall method at depthsca. 4,300 m in an area for dumping industrial waste off Shikoku Island. Since the weight of the largest package was 4,300 kg,
special attention was paid to the connection of a buoyancy system with mooring rope. Descent and ascent velocities of the
free-fall system were calculated prior to the experiment. A free-fall experiment with an extremely heavy object, heavier than
ever previously reported, was accomplished without trouble by using the free-fall system. Recovery of a camera, flash-light,
and other components was successful in each of the three experiments. Successive photographing of the package during descent
was made and its integrity was observed using the photographs taken by the recovered camera. The packages remained intact
during descent and at least for a short time after arrival on the seabed. 相似文献
227.
Haruka Ozawa Kei Hirose Masanori Mitome Yoshio Bando Nagayoshi Sata Yasuo Ohishi 《Physics and Chemistry of Minerals》2009,36(6):355-363
Partitioning of oxygen and silicon between molten iron and (Mg,Fe)SiO3 perovskite was investigated by a combination of laser-heated diamond-anvil cell (LHDAC) and analytical transmission electron
microscope (TEM) to 146 GPa and 3,500 K. The chemical compositions of co-existing quenched molten iron and perovskite were
determined quantitatively with energy-dispersive X-ray spectrometry (EDS) and electron energy loss spectroscopy (EELS). The
results demonstrate that the quenched liquid iron in contact with perovskite contained substantial amounts of oxygen and silicon
at such high pressure and temperature (P–T). The chemical equilibrium between perovskite, ferropericlase, and molten iron at the P–T conditions of the core–mantle boundary (CMB) was calculated in Mg–Fe–Si–O system from these experimental results and previous
data on partitioning of oxygen between molten iron and ferropericlase. We found that molten iron should include oxygen and
silicon more than required to account for the core density deficit (<10%) when co-existing with both perovskite and ferropericlase
at the CMB. This suggests that the very bottom of the mantle may consist of either one of perovskite or ferropericlase. Alternatively,
it is also possible that the bulk outer core liquid is not in direct contact with the mantle. Seismological observations of
a small P-wave velocity reduction in the topmost core suggest the presence of chemically-distinct buoyant liquid layer. Such
layer physically separates the mantle from the bulk outer core liquid, hindering the chemical reaction between them. 相似文献
228.
229.
230.
Hiroko Miyahara Kentaro Nagaya Kimiaki Masuda Yasushi Muraki Hiroyuki Kitagawa Toshio Nakamura 《Quaternary Geochronology》2008,3(3):208-212
In this paper, we review the variation of the 11-year solar cycle since the 15th century revealed by the measurement of radiocarbon content in single-year tree-rings of Japanese cedar trees. Measurements of radiocarbon content in absolutely dated tree-rings provide a calibration curve for accurate dating of archaeological matters, but at the same time, enable us to examine the variations of solar magnetic activity in the pre-historical period. The Sun holds several long-term quasi-cyclic variations in addition to the fundamental 11-year sunspot activity cycle and the 22-year polarity reversal cycle, and it is speculated that the property of the 11-year and the 22-year solar cycle varies in association with such long-term quasi-cycles. It is essential to reveal the details of solar variations around the transition time of solar dynamo for illuminating the mechanisms of the long-term solar variations. We therefore have investigated the property of the 11-year and 22-year cycles around the two grand solar minima; the Maunder Minimum (1645–1715 AD) and the Spoerer Minimum (1415–1534 AD), the periods of prolonged sunspot minima. As a result, slight stretching of the “11-year” and the “22-year” solar cycles was found during these two grand solar activity minima; continuously during the Maunder Minimum and only intermittently during the Spoerer Minimum. On the contrary, normal or slightly shortened 11-year cycles were detected during the interval period of these two minima. It suggests the inverse correlation between the solar cycle length and solar magnetic activity level, and also the change of meridional flow during the grand solar activity minima. Further measurements for the beginning of the grand solar minima will provide a clue to the occurrence of such prolonged sunspot disappearance. We also discuss the effect of solar variations to radiocarbon dating. 相似文献