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541.
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
542.
The relationship between the slip activity and occurrence of historical earthquakes along the Median Tectonic Line (MTL), together with that of the fault systems extending eastward has been examined. The MTL is divided into three segments, each containing diagnostic active faults. No historical earthquakes have been recorded along the central segment, although the segment has faster Quaternary slip rates compared with the other segments that have generated historical earthquakes. This discrepancy between earthquake generation and slip rate can be explained by a microplate model of southwest Japan. The microplate model also provides spatial and temporal coupling of slip on adjacent fault systems. In the context of this model, slip on adjacent faults reduces the normal stress on the MTL. Historical data and paleoseismic evidence indicate that slip on this segment occurs without significant strong ground motion. We interpret this as indicating anomalously slow seismic slip or aseismic slip. Slip on the central segment of the MTL creates transpressional regions at the eastern and western segments where historical earthquakes were recorded. Alternatively, the earthquakes at the eastern and western segments were triggered and concentrated shear stress at the edge of the segments resulted in postseismic slip along the central segment. The sequence of historical events suggests that the MTL characteristically does not produce great earthquakes. The microplate model also provides a tectonic framework for coupling of events among the MTL, the adjacent fault systems and the Nankai trough. 相似文献
543.
544.
Effects of bathymetry on tsunami propagation: Application of ray tracing to tsunamis 总被引:4,自引:0,他引:4
Kenji Satake 《Pure and Applied Geophysics》1988,126(1):27-36
Ray tracing of seismic surface waves is applied to tsunami propagation to examine bathymetric effect along its propagation path. Computations are made for trans-Pacific tsunamis and for near-field tsunamis in the Japan Sea. For tsunamis across the Pacific Ocean, the comparison to a uniform ocean shows that focusing and defocusing, due to bathymetry, are significant for some combinations of source and receiver. For example, the refraction of rays is predominant at the East Pacific Rise for the tsunami from Chile. The tsunamis in the Japan Sea are strongly affected by the shallow Yamato Rise. The predicted arrival time and amplitude distribution generally agree with the observations from an actual tsunami. Since the computation can be made very quickly, the method is useful for preliminary analysis of tsunami propagation, such as in an operational warning system or in the determination of computational area for finite-difference computation. 相似文献
545.
546.
Kenji Bekki 《Astrophysics and Space Science》2001,276(2-4):847-850
When and how red S0 galaxies were formed is a longstanding and noteworthy problem. Recent morphological and photometric studies
of S0sin distant clusters of galaxies have revealed a smaller S0 population fraction and the existence of S0s with bluer colours,
which suggests that some physical processes drive continuous creation of S0s with younger stellar populations in higher-redshift
clusters. We propose here that the major mechanism for S0 creation is galaxy merging between two spirals of unequal masses.
Our numerical simulations demonstrate that galaxy merging exhausts a large amount of the interstellar medium of two gas-rich
spirals owing to the moderately enhanced star formation, and subsequently transforms the two into a single gas-poor S0 galaxy
with structure and kinematics strikingly similar to those observed. This secondary S0 formation via unequal-mass merging thus
provides an evolutionary link between a larger number of blue spirals observed in intermediate-redshift clusters and the red
S0s prevalent in present-day ones.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
547.
Toshitaka Suzuki Yoshinori Iizuka Teruo Furukawa Kenichi Matsuoka Kokichi Kamiyama Okitsugu Watanabe 《极地研究(英文版)》2003,14(1)
1 IntroductionAntarcticicesheetisaburialgroundforatmosphericdeposition .Sincethereiscon tinuousinteractionbetweentheicesheetandtheatmosphere,variousatmosphericsub stancesareinjectedtotheicesheetsequentiallyintimeandspace.Therefore,verticalanalysesoftheicesheetprovideuswithinformationaboutpastclimaticchange (Delmas1 992 ;LegrandandMayewski 1 997)andhorizontalanalysesoftheicesheetprovideuswithknowledgeregardinglong rangetransportofairbornematerials (Kamiyamaetal.1 989;KreutzandMayewski 1 999)… 相似文献
548.
David Kirkman † David Tytler † Nao Suzuki † Carl Melis Susan Hollywood Kory James Geoffrey So Dan Lubin † Tridivesh Jena Michael L. Norman Pascal Paschos 《Monthly notices of the Royal Astronomical Society》2005,360(4):1373-1380
We use high-quality echelle spectra of 24 quasi-stellar objects to provide a calibrated measurement of the total amount of Lyα forest absorption (DA) over the redshift range 2.2 < z < 3.2 . Our measurement of DA excludes absorption from metal lines or the Lyα lines of Lyman-limit systems and damped Lyα systems. We use artificial spectra with realistic flux calibration errors to show that we are able to place continuum levels that are accurate to better than 1 per cent. When we combine our results with our previous results between 1.6 < z < 2.2 , we find that the redshift evolution of DA is well described over 1.6 < z < 3.2 as A (1 + z )γ , where A = 0.0062 and γ= 2.75 . We detect no significant deviations from a smooth power-law evolution over the redshift range studied. We find less H i absorption than expected at z = 3 , implying that the ultraviolet background is ∼40 per cent higher than expected. Our data appears to be consistent with an H i ionization rate of Γ∼ 1.4 × 10−12 s−1 . 相似文献
549.
Summary ?Hydrothermal experiments to synthesize pumpellyite group minerals of the pumpellyite–okhotskite series and to investigate
their stability have been carried out at 200, 300 and 400 MPa P
fluid and 250–500 °C by using cold-seal pressure vessels and solid buffers of MnO2–Mn2O3, Cu2O–CuO and Cu2O–Cu buffer assemblages. Okhotskite and pumpellyite rich in the okhotskite component crystallized from an oxide mixture starting
material of Ca4MgMn3+
3Al2Si6O24.5-oxide+excess H2O at P
fluid of 200, 300 and 400 MPa and temperatures of 300 and 400 °C. However, a single phase of okhotskite was not produced, and associated
piemontite, hausmannite, wollastonite, clinopyroxene, corundum, braunite–neltnerite solid solution and alleghanyite also formed.
Mn-pumpellyite of the okhotskite–pumpellyite join occurs as aggregates of needle crystals, rounded grains or flaky crystals.
Chemical compositions are variable and range from pumpellyite-(Mn2+) to okhotskite: 31–36 SiO2, 13–21 Al2O3, 12–25 total Mn2O3, 0.6–4 MgO and 20–24 wt.% CaO. Reconnaissance experiments using a starting material of synthetic Ca2Mn3+Al2Si3O12(OH)-piemontite at 300 MPa and temperatures of 250, 300, 400 and 500 °C indicate that Mn-rich pumpellyite can crystallize
from piemontite at lower temperatures than the stability field of piemontite. The Mn-rich pumpellyite was accompanied by garnet,
wollastonite and alleghanyite. The chemical compositions of the Mn-pumpellyites are 32–36 SiO2, 18–27 Al2O3, 8–18 total Mn2O3 and 20–23 wt.% CaO. This study shows that the stability fields of piemontite, piemontite+Mn-pumpellyite, and Mn-pumpellyite
range in this order with decreasing temperature under high fO2 conditions. The maximum stability temperature of Mn-rich pumpellyite lies between 400 and 500 °C at 200–400 MPa in high fO2 conditions.
Received March 3, 2000; revised version accepted December 28, 2001 相似文献
550.
Hossain Md. Shahin Teruo Nakai Kenji Ishii Toshikazu Iwata Shou Kuroi 《Acta Geotechnica》2016,11(3):679-692
To investigate the realistic ground behavior during tunneling, a new device has been developed. With the new device, model tests of tunnel excavation considering an existing tunnel and an existing building were carried out. Non-linear finite element analyses corresponding to the model tests were also conducted using FEMtij-2D software where an elastoplastic subloading t ij model was used to describe the mechanical behavior of soil. Earth pressure distribution around the tunnels and ground movements during tunnel excavation depend on the distance and position between the twin tunnels. There is a significant effect of tunneling on the existing foundation of building even in the case where the tunnel is constructed in deep underground. The numerical analyses capture well the results of the model tests. 相似文献