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201.
Tetsuya Takahashi Hideaki Nakata Keiji Hirano Kazumi Matsuoka Mitsunori Iwataki Hitoshi Yamaguchi Tomoyuki Kasuya 《Journal of Oceanography》2009,65(1):113-120
Wind-induced circulation and the distribution of hypoxia corresponding to the upwelling of oxygen-depleted water (called “Aoshio”
in Japan and “Sumishio” locally in Omura Bay) in Omura Bay, Japan, was examined field observations and by three-dimensional
modeling. During the calm weather in summer, well-mixed strait water, in rich oxygen at the mouth of the bay intruded into
the middle layer of the bay, southward and northward along the west and east coast, respectively, forming basin-scale cyclonic
circulation. A stagnant water mass was formed below the center of this cyclonic circulation, and it became hypoxic water.
As a result of the prevailing strong southeast (northeast) wind, the bottom hypoxia moved in a southeasterly (northeasterly)
direction. This induces the upwelling of hypoxic water, accompanied by mass mortality of marine organisms. 相似文献
202.
Akira Mizuta Jave O. Kane Marc W. Pound Bruce A. Remington Dmitri D. Ryutov Hideaki Takabe 《Astrophysics and Space Science》2007,307(1-3):183-186
Hydrodynamic instability of an accelerating ionization front (IF) is investigated with 2D hydrodynamic simulations, including
absorption of incident photoionizing photons, recombination in the HII region, and radiative molecular cooling. When the amplitude
of the perturbation is large enough, nonlinear dynamics of the IF triggered by the separation of the IF from the cloud surface
is observed. This causes the second harmonic of the imposed perturbation to appear on the cloud surfaces, whereas the perturbation
in density of ablated gas in the HII region remains largely single mode. This mismatch of modes between the IF and the density
perturbation in the HII region prevents the strong stabilization effect seen in the linear regime. Large growth of the perturbation
caused by Rayleigh-Taylor-like instability is observed late in time. 相似文献
203.
L. Gao N. Yoshida T. Abel C. S. Frenk A. Jenkins V. Springel 《Monthly notices of the Royal Astronomical Society》2007,378(2):449-468
We have performed a large set of high-resolution cosmological simulations using smoothed particle hydrodynamics to study the formation of the first luminous objects in the Lambda cold dark matter cosmology. We follow the collapse of primordial gas clouds in eight early structures and document the scatter in the properties of the first star-forming clouds. Our first objects span formation redshifts from z ∼ 10 to ∼50 and cover an order of magnitude in halo mass. We find that the physical properties of the central star-forming clouds are very similar in all of the simulated objects despite significant differences in formation redshift and environment. This suggests that the formation path of the first stars is largely independent of the collapse redshift; the physical properties of the clouds have little correlation with spin, mass or assembly history of the host halo. The collapse of protostellar objects at higher redshifts progresses much more rapidly due to the higher densities, which accelerates the formation of molecular hydrogen, enhances initial cooling and shortens the dynamical time-scales. The mass of the star-forming clouds cover a broad range, from a few hundred to a few thousand solar masses, and exhibit various morphologies: some have disc-like structures which are nearly rotational supported; others form flattened spheroids; still others form bars. All of them develop a single protostellar 'seed' which does not fragment into multiple objects up to the moment that the central gas becomes optically thick to H2 cooling lines. At this time, the instantaneous mass accretion rate on to the centre varies significantly from object to object, with disc-like structures having the smallest mass accretion rates. The formation epoch and properties of the star-forming clouds are sensitive to the values of cosmological parameters. 相似文献
204.
205.
Kohki Yoshida Toru Nakajima Yuki Matsumoto Ai Osaki Lalit Kumar Rai Jarrett W. Cruz Harutaka Sakai 《Island Arc》2021,30(1):e12408
Bengal Fan Miocene sediments were collected during International Ocean Discovery Program Expedition 354 and investigated using petrographic and detrital garnet chemistry analyses. The Miocene Siwalik Group, which is composed of sediments deposited in the Himalayan foreland basin, was also analyzed for comparison with the Bengal Fan data for the provenance change during the Miocene. Our petrographic analyses revealed that the Miocene sediments of the Bengal Fan and Siwalik Group consist predominantly of Higher Himalayan Crystalline (HHC)-derived detritus such as chloritoid, staurolite, sillimanite, and/or kyanite, which appear among the accessory minerals. The chemistry of the detrital garnet varies across the stratigraphy; most of the garnet is rich in almandine and poor in spessartine and pyrope. However, pyrope-rich garnet, which is considered to originate from the HHC core (granulite facies), was found in the lower to upper Miocene deposits. The deposition of HHC-derived detrital garnet began before the Middle Miocene (15 Ma) and before the Late Miocene (10–9 Ma) in the Siwalik Group. The Bengal Fan data, by contrast, indicated that pyrope-rich garnet appeared in the Early Miocene (17.3 Ma) and Late Miocene (8.5–6.5 Ma). We conclude that the Bengal Fan sediments record the erosion of the HHC zone since the Early Miocene that appears in the Siwalik sediments. Furthermore, we found that the HHC-derived inputs decreased from the late Middle Miocene (12 Ma) to the early Middle Miocene (10 Ma) in both the Nepal Himalaya foreland basin and the Bengal Fan. The disappearance of the HHC-derived detritus is probably the result of dilution by Lesser Himalayan detritus, which suggests that the Lesser Himalayan zone, which is composed of metamorphosed and unmetamorphosed sedimentary rocks, was uplifted. 相似文献
206.
207.
Tsuyoshi Yoshioka Michinobu Furukawa Koji Yoshizaki Ryuji Matsuhashi Yoshikuni Yoshida 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(5):677-683
Recently, energy service providers (ESP) have increased due to deregulation in the power market. They install energy supply
equipment at their own cost and supply the necessary energy to the client. The Tokyo Metropolitan Government started Asia’s
first cap-and-trade program in April 2010. This program caps energy-related carbon dioxide emissions from some 1,330 offices
and factories in Tokyo. Then, ESPs have to manage the many risks of energy service project directly linked to the profits.
In this paper, we describes the risk analysis and investment optimization for energy service projects using financial engineering. 相似文献
208.
209.
Microbial community respiration and structure of dead zone sediments of Omura Bay, Japan 总被引:1,自引:0,他引:1
Minoru Wada Shotaro Suzuki Tadashi Nara Yu Umezawa Motohiro Shimanaga Kazumi Matsuoka Hideaki Nakata 《Journal of Oceanography》2012,68(6):857-867
Monitoring sediment microbial community metabolism and structure is instrumental to understanding biogeochemical processes in and ecological impacts on bottom environments. The aim of this study was to determine potential community respiration and to reveal community dynamics of the microorganisms in the dead zone sediments of Omura Bay, Japan. The bay is highly enclosed and develops severe hypoxia in the central regions every summer. We collected sediment core samples from the center of the bay during hypoxia, estimated sediment oxygen consumption by using an adapted in vivo electron transport system activity (in vivo ETSA) assay, enumerated abundance of bacteria, and analyzed bacterial community structure by automated ribosomal intergenic spacer analysis. Higher ETSA and bacterial diversity were found in upper sediments (within 3?cm depth) from the center than the fringe of the bay. Sediment bacterial community structure of the bay center was distinct from that of the fringe. From these results, upper sediment in the dead zone of Omura Bay was characterized by (1) greater community respiration and (2) greater diversity of bacterial components compared with the non-hypoxic sediment of the bay fringe. These characteristics have important implications for understanding the interaction between microbial communities and the development of hypoxia in Omura Bay. 相似文献
210.
Koichiro Doi Hideaki Hayakawa Takahito Kazama Toshihiro Higashi Shingo Osono Yoichi Fukuda Jun Nishijima Yuichi Aoyama Junichi Ueda 《极地研究(英文版)》2013,(4):339-343
Abstract This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the framework of the 53rd Japanese Antarctic Research Expedition (JARE53). Absolute gravity measurements, together with GPS measurements, were planned at several outcrops along the Prince Olav Coast and S6ya Coast of East Antarctica, including at Syowa Station. Since the icebreaker Shirase (AGB 5003) was unable to moor alongside Syowa Station, operations were somewhat restricted during JARE53. However, despite this setback, we were able to complete measurements at two sites: Syowa Station and Langhovde. The absolute gravity value at the Syowa Station IAGBN (A) site, observed using an FG-5 absolute gravimeter (serial number 210; FG-5 #210), was 982 524 322.7+0.1 ktGal, and the gravity change rate at the beginning of 2012 was -0.26 gGal.a-1. An absolute gravity value of 982 535 584.2~0.7 ktGal was obtained using a portable A-10 absolute gravimeter (serial number 017; A-10 #017) at the newly located site AGS01 in Langhovde. 相似文献