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21.
Hidenobu Yajima Masayuki Umemura Masao Mori Taishi Nakamoto 《Monthly notices of the Royal Astronomical Society》2009,398(2):715-721
In order to assess the contribution of Lyman break galaxies (LBGs) and Lyman α emitters (LAEs) at redshifts 3 < z < 7 to the ionization of intergalactic medium (IGM), we investigate the escape fractions of ionizing photons from supernova-dominated primordial galaxies by solving the three-dimensional (3D) radiative transfer. The model galaxy is employed from an ultra-high-resolution chemodynamic simulation of a primordial galaxy by Mori & Umemura, which well reproduces the observed properties of LAEs and LBGs. The total mass of model galaxy is 1011 M⊙ . We solve not only photoionization but also collisional ionization by shocks. In addition, according to the chemical enrichment, we incorporate the effect of dust extinction, taking the size distributions of dust into account. As a result, we find that dust extinction reduces the escape fractions by a factor of 1.5–8.5 in the LAE phase and by a factor of 2.5–11 in the LBG phase, while the collisional ionization by shocks increases the escape fractions by a factor of ≈2 . The resultant escape fractions are 0.07–0.47 in the LAE phase and 0.06–0.17 in the LBG phase. These results are well concordant with the recent estimations derived from the flux density ratio at 1500 to 900 Å of LAEs and LBGs. Combining the resultant escape fractions with the luminosity functions of LAEs and LBGs, we find that high- z LAEs and LBGs can ionize the IGM at z = 3–5 . However, ionizing radiation from LAEs as well as LBGs falls short of ionizing the IGM at z > 6 . That implies that additional ionization sources may be required at z > 6 . 相似文献
22.
Kana NAGASHIMA Masayuki NARA Jun‐ichi MATSUDA 《Meteoritics & planetary science》2012,47(11):1728-1737
Abstract– We performed micro‐Raman spectroscopic analyses of the carbon vein in five ureilites: Allan Hills (ALH) A77257, Northwest Africa (NWA) 3140, Shi?r 007, Yamato 790981 (Y‐790981), and Yamato 791538 (Y‐791538). The graphite peaks showed that the graphite structure in ureilite is well developed, especially compared with the carbonaceous material in carbonaceous chondrite. The domain sizes of the graphite were 45–110 Å. We observed shifts in the diamond peak positions to higher wave numbers with a large full width at half maximum (FWHM), especially for NWA 3140. Although the FWHM of a diamond peak is not a crucial diagnostic test for a chemical vapor deposition (CVD) origin of diamond, the shift of the diamond peaks to higher wave numbers could be a strong indicator that supports the CVD origin as these shifts have only been observed in CVD diamonds. We discuss the origin of diamond from various aspects, and confirm that the CVD model is the most plausible. We conclude that all carbon material (graphite, amorphous carbon, diamond, etc.) condensed on the early condensates in the primitive solar nebula. 相似文献
23.
24.
Finite‐element analysis of laminated rubber bearing of building frame under seismic excitation 下载免费PDF全文
Makoto Ohsaki Tomoshi Miyamura Masayuki Kohiyama Takuzo Yamashita Masashi Yamamoto Naohiro Nakamura 《地震工程与结构动力学》2015,44(11):1881-1898
Finite element analysis is carried out for a building frame supported by laminated rubber bearings to simultaneously investigate global displacement and local stress responses under seismic excitation. The frame members and the rubber bearings are discretized into hexahedral solid elements with more than 3 million degrees of freedom. The material property of rubber is represented by the Ogden model, and the frame is assumed to remain in elastic range. It is shown that the time histories of non‐uniform stress distribution and rocking behavior of the rubber bearings under a frame subjected to seismic excitation can be successfully evaluated, and detailed responses of base and frame can be evaluated through large‐scale finite element analysis. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
25.
Takami Morita Shigeyoshi Otosaka Kou Nishiuchi Haruya Yamada Masayuki Minakawa 《Marine pollution bulletin》2010,60(8):1193-1199
60Co were detected in common octopus specimens collected in the East China Sea in 1996-2005. The source of 60Co has remained unclear yet. Stable isotope analyses showed that there was no difference in stable Co concentrations between octopus samples with 60Co and without 60Co. This result showed that the stable Co in the digestive gland of octopus potentially did not include a trace amount of 60Co and the source of 60Co existed independently. Furthermore, investigations of octopus in other area and other species indicated that the origin of the source of 60Co occurred locally in the restricted area in the East China Sea and not in the coastal area of Japan. Concentrations of 60Co have annually decreased with shorter half-life than the physical half-life. This decrease tendency suggests that the sources of 60Co were identical and were temporary dumped into the East China Sea as a solid waste. 相似文献
26.
We study the ground motion simulations based on three finite-source models for the 2007 Mw6.6 Niigata Chuetsu-oki, Japan, earthquake in order to discuss the performance of the input ground motion estimations for the near-field seismic hazard analysis. The three models include a kinematic source inverted from the regional accelerations, a dynamic source on a planar fault with three asperities inferred from the very-near-field ground motion particle motions, and another dynamic source model with conjugate fault segments. The ground motions are calculated for an available 3D geological model using a finite-difference method. For the comparison, we apply a goodness-of-fit score to the ground motion parameters at different stations, including the nearest one that is almost directly above the ruptured fault segments. The dynamic rupture models show good performance. We find that seismologically inferred earthquake asperities on a single fault plane can be expressed with two conjugate segments. The rupture transfer from one segment to another can generate a significant radiation; this could be interpreted as an asperity projected onto a single fault plane. This example illustrates the importance of the fault geometry that has to be taken into account when estimating the very-near-field ground motion. 相似文献
27.
分辨多数余震和后续主震是由静态应力触发(Stein,1999;Todaetal,2005;Parsons,2002)还是动态应力触发(Hilletal,1993;kilb,2003;Brodsky and Prejean,2005;Gomberg and Johnson,2005;Hill and Prejean,2007),对理解地震内在作用和预测地震危险性是有必要的(Freed,2005)。Felzer和Brodsky(2006)分析了2≤M<3和3≤M<4级主震后5min内余震的空间分布情况,发现距主震50km范围内M≥2余震具有特定的幂律衰减关系,且衰减曲线的斜率为-1.35。据此,他们认为余震随距离的衰减只能用动态触发来解释。基于上述假设我们进行了一系列的检验,但没有一个可通过检验,进而,本文中对这种衰减关系提出了另外一种解释。在距离2≤M<3主震300m以外的地方,主震前5min内的地震活动性衰减与主震后5min内的衰减没有显著的区别,表明主震对它静态触发区域以外的地方没有影响。表征余震基本特性的大森随时间衰减关系在距离主震10km以外的地方是不存在的。最后,发现在主震波前未到达之前的余震中发现了... 相似文献
28.
Motoyoshi Oda Shun Chiyonobu Masayuki Torii Takashi Otomo Jumpei Morimoto Yuri Satou Hiroshi Ishikawa Matsuaki Ashikawa Osamu Tominaga 《Journal of Asian Earth Sciences》2011,40(1):84-97
An integrated magnetobiochronology of the Miyazaki Pliocene–Pleistocene succession in the Miyazaki area, southwest Japan, was established using planktic foraminiferal and calcareous nannofossil biostratigraphy together with paleomagnetic data. The upper Miyazaki succession in the northern Miyazaki region can be divided into the Takanabe, Hisamine (redefined), and Higoyashiki (new) Formations, in ascending order. A depositional hiatus between the Hisamine Formation and the Takanabe and/or older formations was also identified based on integrated magnetobiostratigraphy from five sections including the Nagatani River (NGT) section through the uppermost Miyazaki succession. The hiatus, herein called the Hisamine unconformity, is equivalent to the Kurotaki unconformity between the Miura and Kazusa groups of the Boso Peninsula in central Japan. The depositional hiatus recognised in the lower Pleistocene of Pacific coastal areas in southwestern and central Japan may have resulted from tectonic activity associated with a change in the subduction direction of the Philippine Sea plate, which commenced prior to ca. 2.2 Ma. The youngest unit just below the hiatus is the upper part of the Takanabe Formation in the NGT section. The NGT section represents the continuous Late Pliocene to earliest Pleistocene sequence including the Gauss/Matuyama boundary and is here proposed as the type section for the Pliocene/Pleistocene boundary in Japan, which the IUGS ratified as the base of the Gelasian in 2009. 相似文献
29.
Hisanari Sugawara Masayuki Sakakibara David Belton Tetsuya Suzuki 《Environmental Earth Sciences》2013,69(3):811-819
Pyrite framboid in sedimentary rocks could be concerned with arsenic contamination in groundwater of acidic environment and has been studied for the formation process of its unique morphology. However, not much has been discussed about the formation process based on the heavy-metal distribution in pyrite framboids and their aggregates. To reveal the formation process of pyrite framboids and their aggregates, mudstone from the Late Cretaceous Hakobuchi Group, central Hokkaido, Japan, are investigated for mode, petrographical, mineralogical, and micro-PIXE (particle-induced X-ray emission) analysis in this study. Spherical and sub-spherical pyrite framboids observed in polyframboids can be divided into two types based on the diameter of framboids (D) and the average diameter of microcrystals (d) within framboids: type 1, ranging from 2 to 9 μm and from 0.4 to 0.9 μm, respectively, and type 2, ranging from 8 to 50 μm and from 0.5 to 1.8 μm, respectively. Based on the quantitative traverse analyses and 2-D elemental mapping results by micro-PIXE, heterogeneities in the concentrations of heavy metals within the analyzed aggregations of pyrite are exhibited. On the basis of the As and Pb zoning patterns, the time range and chronological stages of pyrite-aggregation growth are revealed. 相似文献
30.
Shoichi Yoshioka Mamiko Toda Junichi Nakajima 《Earth and Planetary Science Letters》2008,272(1-2):189-198
The Fukuoka District Meteorological Observatory recently logged three possible deep low-frequency earthquakes (LFEs) beneath eastern Kyushu, Japan, a region in which LFEs and low-frequency tremors have never before been identified. To assess these data, we analyzed band-pass filtered velocity seismograms and relocated LFEs and regular earthquakes using the double-difference method. The results strongly suggest that the three events were authentic LFEs, each at a depth of about 50 km. We also performed relocation analysis on LFEs recorded beneath the Kii Peninsula and found that these LFEs occurred near the northwest-dipping plate interface at depths of approximately 29–38 km. These results indicate that LFEs in southwest Japan occur near the upper surface of the subducting Philippine Sea (PHS) plate. To investigate the origin of regional differences in the occurrence frequency of LFEs in western Shikoku, the Kii Peninsula, and eastern Kyushu, we calculated temperature distributions associated with PHS plate subduction. Then, using the calculated thermal structures and a phase diagram of water dehydration for oceanic basalt, the water dehydration rate (wt.%/km), which was newly defined in this study, was determined to be 0.19, 0.12, and 0.08 in western Shikoku, the Kii Peninsula, and eastern Kyushu, respectively; that is, the region beneath eastern Kyushu has the lowest water dehydration rate value. Considering that the Kyushu–Palau Ridge that is subducting beneath eastern Kyushu is composed of tonalite, which is low in hydrous minerals, this finding suggests that the regionality may be related to the amount of water dehydration associated with subduction of the PHS plate and/or differences in LFE depths. Notable dehydration reactions take place beneath western Shikoku and the Kii Peninsula, where the depth ranges for dehydration estimated by thermal modeling agree well with those for the relocated LFEs. The temperature range in which LFEs occur in these regions is estimated to be 400–500 °C. 相似文献