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401.
402.
Kenya Ohgushi Yoshitaka Matsushita Nobuyoshi Miyajima Yoshio Katsuya Masahiko Tanaka Fujio Izumi Hirotada Gotou Yutaka Ueda Takehiko Yagi 《Physics and Chemistry of Minerals》2008,35(4):189-195
Structural, morphological, magnetic, and thermal properties have been investigated for a novel post-perovskite oxide CaPtO3 synthesized under high pressure. By comparing obtained structural parameters with those for known post-perovskite compounds,
we argue that the chemical bond has a strong covalent character. Precise measurements of the Langevin susceptibility χ
0
= −9.6 × 10−5 emu/mol and Debye temperature θ ∼ 470 K provide a good opportunity to confirm the reliability of first-principle calculations on predicting physical properties
of the Earth’s D” layer. 相似文献
403.
At various stages of petroleum reservoir development, we encounter a large degree of geological uncertainty under which a rational decision has to be made. In order to identify which parameter or group of parameters significantly affects the output of a decision model, we investigate decision-theoretic sensitivity analysis and its computational issues in this paper. In particular, we employ the so-called expected value of partial perfect information (EVPPI) as a sensitivity index and apply multilevel Monte Carlo (MLMC) methods to efficient estimation of EVPPI. In a recent paper by Giles and Goda, an antithetic MLMC estimator for EVPPI is proposed and its variance analysis is conducted under some assumptions on a decision model. In this paper, for an improvement on the performance of the MLMC estimator, we incorporate randomized quasi-Monte Carlo methods within the inner sampling, which results in an multilevel quasi-Monte Carlo (MLQMC) estimator. We apply both the antithetic MLMC and MLQMC estimators to a simple waterflooding decision problem under uncertainty on absolute permeability and relative permeability curves. Through numerical experiments, we compare the performances of the MLMC and MLQMC estimators and confirm a significant advantage of the MLQMC estimator. 相似文献
404.
Towhata Ikuo Goto Satoshi Goto Shigeru Akima Takeshi Tanaka Junya Uchimura Taro Wang Gonghui Yamaguchi Hiroshi Aoyama Shogo 《Natural Hazards》2021,105(1):501-530
Natural Hazards - A volcanic slope in Izu Oshima Island in Japan experienced a profound rain-induced disaster in October 2013. Since this slope had been stable for centuries except for minor... 相似文献
405.
As planetary embryos grow, gravitational stirring of planetesimals by embryos strongly enhances random velocities of planetesimals and makes collisions between planetesimals destructive. The resulting fragments are ground down by successive collisions. Eventually the smallest fragments are removed by the inward drift due to gas drag. Therefore, the collisional disruption depletes the planetesimal disk and inhibits embryo growth. We provide analytical formulae for the final masses of planetary embryos, taking into account planetesimal depletion due to collisional disruption. Furthermore, we perform the statistical simulations for embryo growth (which excellently reproduce results of direct N-body simulations if disruption is neglected). These analytical formulae are consistent with the outcome of our statistical simulations. Our results indicate that the final embryo mass at several AU in the minimum-mass solar nebula can reach about ∼0.1 Earth mass within 107 years. This brings another difficulty in formation of gas giant planets, which requires cores with ∼10 Earth masses for gas accretion. However, if the nebular disk is 10 times more massive than the minimum-mass solar nebula and the initial planetesimal size is larger than 100 km, as suggested by some models of planetesimal formation, the final embryo mass reaches about 10 Earth masses at 3-4 AU. The enhancement of embryos’ collisional cross sections by their atmosphere could further increase their final mass to form gas giant planets at 5-10 AU in the Solar System. 相似文献
406.
Naoki Ikegaya Aya Hagishima Jun Tanimoto Yudai Tanaka Ken-ichi Narita Sheikh Ahmad Zaki 《Boundary-Layer Meteorology》2012,143(2):357-377
We performed a series of wind-tunnel experiments under neutral conditions in order to create a comprehensive database of scalar
transfer coefficients for street surfaces using regular block arrays representing an urban environment. The objective is to
clarify the geometric dependence of scalar transfer phenomena on rough surfaces. In addition, the datasets we have obtained
are necessary to improve the modelling of scalar transfer used for computational simulations of urban environments; further,
we can validate the results obtained by numerical simulations. We estimated the scalar transfer coefficients using the salinity
method. The various configurations of the block arrays were designed to be similar to those used in a previous experiment
to determine the total drag force acting on arrays. Our results are summarized as follows: first, the results for cubical
arrays showed that the transfer coefficients for staggered and square layouts varied with the roughness packing density. The
results for the staggered layout showed the possibility that the mixing effect of air can be enhanced for the mid-range values
of the packing density. Secondly, the transfer coefficients for arrays with blocks of non-uniform heights were smaller than
those for arrays with blocks of uniform height under conditions of low packing density; however, as the packing density increased,
the opposite tendency was observed. Thirdly, the randomness of rotation angles of the blocks in the array led to increasing
values of the transfer coefficients under sparse packing density conditions when compared with those for cubical arrays. 相似文献
407.
408.
Wind-Tunnel Experiment on Logarithmic-Layer Turbulence under the Influence of Overlying Detached Eddies 总被引:1,自引:1,他引:0
Yasuo Hattori Chin-Hoh Moeng Hitoshi Suto Nobukazu Tanaka Hiromaru Hirakuchi 《Boundary-Layer Meteorology》2010,134(2):269-283
A wind-tunnel experiment was carried out to test a hypothesis that the turbulence characteristics in the near-neutral surface
layer are largely determined by detached eddies from above. The surrogate detached eddies were generated by using an active
turbulence grid installed at the front of the test section and the parameters of the grid were chosen such that the fully
developed logarithmic layer downstream consists of a turbulent flow that has similar normalized intensity to that typically
observed in the near-neutral atmospheric surface layer. The effects of the detached eddies on turbulence characteristics were
investigated by comparison with a second experiment without detached eddies. The influence of the detached eddies on the logarithmic
layer was mostly on the coherent structures; the logarithmic layer with the detached eddies revealed a multi-layer structure
similar to that found in the atmosphere where the lower part of the surface layer is dominated by sweep-like events and the
upper part by ejection-like events. Our experiments show that the mean velocity gradient and the Reynolds shear stress were,
however, not affected significantly by the detached eddies and hence the eddy viscosity. 相似文献
409.
Søren-Aksel Sørensen Takyua Matsuda Takeo Sakurai 《Astrophysics and Space Science》1975,33(2):465-480
A gas-dynamical model of gas streams around close binary systems is given. The velocity feld and the density distribution are determined for different parameter ranges. The results succeed in explaining the formation of a ring and a disk around the accreting component. The models furthermore reveal the existence of a tongue of matter extending from the inner Lagrangian point and a jet perpendicular to the system axis. 相似文献
410.