Cosmological radiative transfer codes comparison project – I. The static density field tests     

Ilian T. Iliev  Benedetta Ciardi  Marcelo A. Alvarez  Antonella Maselli  rea Ferrara  Nickolay Y. Gnedin  Garrelt Mellema  Taishi Nakamoto  Michael L. Norman  Alexei O. Razoumov  Erik-Jan Rijkhorst  Jelle Ritzerveld  Paul R. Shapiro  Hajime Susa  Masayuki Umemura  Daniel J. Whalen 《Monthly notices of the Royal Astronomical Society》2006,371(3):1057-1086

Radiative transfer (RT) simulations are now at the forefront of numerical astrophysics. They are becoming crucial for an increasing number of astrophysical and cosmological problems; at the same time their computational cost has come within reach of currently available computational power. Further progress is retarded by the considerable number of different algorithms (including various flavours of ray tracing and moment schemes) developed, which makes the selection of the most suitable technique for a given problem a non-trivial task. Assessing the validity ranges, accuracy and performances of these schemes is the main aim of this paper, for which we have compared 11 independent RT codes on five test problems: (0) basic physics; (1) isothermal H  ii region expansion; (2) H  ii region expansion with evolving temperature; (3) I-front trapping and shadowing by a dense clump and (4) multiple sources in a cosmological density field. The outputs of these tests have been compared and differences analysed. The agreement between the various codes is satisfactory although not perfect. The main source of discrepancy appears to reside in the multifrequency treatment approach, resulting in different thicknesses of the ionized-neutral transition regions and the temperature structure. The present results and tests represent the most complete benchmark available for the development of new codes and improvement of existing ones. To further this aim all test inputs and outputs are made publicly available in digital form.  相似文献   

Assessment of potential outburst floods from the Tsho Rolpa glacial lake in Nepal   总被引：1，自引：1，他引：0  

Badri Bhakta Shrestha  Hajime Nakagawa 《Natural Hazards》2014,71(1):913-936

Flood and sediment disasters caused by glacial lake outbursts have occurred frequently in recent years in the Himalayas of Nepal. Glacial lake outburst floods (GLOFs) can cause catastrophic flooding in downstream areas with serious damage to lives and property. It is thus important to investigate outburst floods from potentially dangerous glacial lakes. In this study, the characteristics of potential outburst floods from the Tsho Rolpa glacial lake due to two types of moraine dam failure caused by seepage flow or water overtopping were analyzed with various scenarios by using integrated modeling system of three numerical models: (1) the flow and bed-surface erosion model, (2) the seepage model and (3) the slope stability model. Flood inundation areas were also identified by using the numerical model of the flow and moraine dam failure and geographical information system tools. Possible threats and damages due to the potential GLOF events from the lake were also analyzed based on numerical results, flood inundation maps and field investigations.  相似文献   

Thermal Wind Balance with Full Geostrophy: Comments on "Large Scale Geostrophic Winds with a full Representation of the Coriolis Force: Application to IR Observations of the Upper Jovian Troposphere" by M. de la Torre Juarez,B.M. Fisher and G.S. Orton     

Jun-Ichi Yano 《地球物理与天体物理流体动力学》2013,107(5):425-429

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Dissolved iron and zinc in Sagami Bay and the Izu-Ogasawara Trench     

Hajime Obata  Jun Nishioka  Taejin Kim  Kazuhiro Norisuye  Shigenobu Takeda  Yohei Wakuta  Toshitaka Gamo 《Journal of Oceanography》2017,73(3):333-344

Using a clean seawater sampling system for trace metals onboard the R. V. Shinsei-Maru, newly launched in 2013, we investigated the vertical distributions of dissolved iron and zinc in Sagami Bay and the Izu-Ogasawara Trench. We applied appropriate clean sampling and filtering processes for trace metals, so that uncontaminated seawater samples were successfully collected. The distribution of zinc in the trench area was similar to that of silicate and the same as that previously reported in the subtropical North Pacific. There were spatial variations in the iron (Fe) distribution in the trench areas. We used previously reported information about biogeochemical cycling in the trench area, and found that Fe has a residence time of 29 years in the water column. The short residence time of Fe (29 years) corresponds to the vertical variations of dissolved Fe in the water column.  相似文献   

尼罗河及其流域环境的近期变化：以文献为依据     

Shamik CHAKRABORTY  YASUDA Hiroshi  Abhik CHAKRABORTY  NABETA Hajime  KAWAI Takayuki  ISHIYAMA Shun 《资源与生态学报(英文版)》2015,6(5):345-352

The Nile is one of the longest rivers on the planet and an important freshwater source for the arid regions of Africa. It is also a river that is extensively affected by anthropogenic impact. This paper aims to provide an account of the social drivers that combine to cause extensive changes in the Nilotic environments. This paper is based on extensive review of literature backed up by field research. The main focus is on the lower Nile, where the effects of anthropogenic disturbances are most prominent. We argue that the Nile Basin is characterized by interrelated and compound problems of resource management, and managing this river system effectively requires shifting the focus from water related problems to a basin wide management agenda. We contend that knowledge of environmental history is important for this agenda shift, and the idea of benefit sharing can alleviate the growing stress on this extremely sensitive arid river basin.  相似文献   

PetraSim: A Graphical User Interface for the TOUGH2 Family of Multiphase Flow and Transport Codes     

Hajime Yamamoto 《Ground water》2008,46(4):525-528

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Extracellular release of β-lactamase by osmotic shock inSynechococcus transformant     

Yano  Shin-ichi  Kawata  Yoshikazu  Kojima  Hiroyuki 《中国海洋湖沼学报》1998,16(1):105-108

A unicellular cyanobacteriumSynechococcus sp. strain PCC 7002 was transformed with plasmid pQL1, on which β-lactamase gene (bla) and β-galactosidase gene (lacZ) were encoded. The transformant cells released β-lactamase into medium by an abrupt drop of osmotic pressure. This result indicates that this cyanobacterium recognizes and processes the signal sequence of β-lactamase, and accumulates the enzyme in periplasm. Repeated release of β-lactamase was possible by repeated osmotic shocks wihout, impairing cell viability. On the other hand, most of the β-galactosidase remained in cytoplasm under the osmotic shock.

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V p/V s-ratios from the central Kolbeinsey Ridge to the Jan Mayen Basin,North Atlantic; implications for lithology,porosity and present-day stress field     

Mjelde  Rolf  Aurvåg  Roar  Kodaira  Shuichi  Shimamura  Hideki  Gunnarsson  Karl  Nakanishi  Ayako  Shiobara  Hajime 《Marine Geophysical Researches》2002,23(2):123-145

The horizontal components from twenty Ocean Bottom Seismometers deployed along three profiles near the Kolbeinsey Ridge, North Atlantic, have been modelled with regard to S-waves, based on P-wave models obtained earlier. Two profiles were acquired parallel to the ridge, and the third profile extended eastwards across the continental Jan Mayen Basin. The modelling requires a thin (few 100 m) layer with very high V _p/V _s-ratio (3.5–9.5) at the sea-floor in the area lacking sedimentary cover. The obtained V _p/V _s-ratios for the remaining part of layer 2A, 2B, 3 and upper mantle, correspond to the following lithologies: pillow lavas, sheeted dykes, gabbro and peridotite, respectively. All crustal layers exhibit a decreasing trend in V _p/V _s-ratio away-from-the-axis, interpreted as decreasing porosity and/or crack density in that direction. A significant S-wave azimuthal anisotropy is observed within the thin uppermost layer of basalt near the ridge. The anisotropy is interpreted as being caused by fluid-filled microcracks aligned along the direction of present-day maximum compressive stress, and indicates crustal extension at the ridge itself and perpendicular-to-the-ridge compression 12 km off axis. Spreading along the Kolbeinsey Ridge has most likely been continuous since its initiation ca. 25 Ma: The data do not suggest the presence of an extinct spreading axis between the Kolbeinsey Ridge and the Aegir Ridge as has been proposed earlier. The V _p/V _s-ratios found in the Jan Mayen Basin are compatible with continental crust, overlain by a sedimentary section dominated by shale.  相似文献   

Lower crustal seismic velocity-anomalies; magmatic underplating or serpentinized peridotite? Evidence from the Vøring Margin,NE Atlantic     

Mjelde  Rolf  Kasahara  Junzo  Shimamura  Hideki  Kamimura  Aya  Kanazawa  Toshihiko  Kodaira  Shuichi  Raum  Thomas  Shiobara  Hajime 《Marine Geophysical Researches》2002,23(2):169-183

On the Vøring volcanic passive margin offshore mid-Norway, NE Atlantic, a lower crustal body with P-wave velocities in the range of 7.1–7.7 km/s has been mapped by twenty two-dimensional Ocean Bottom Seismograph (OBS) profiles. The main aim of the present paper is to evaluate to what extent the lower crust is consistent with magmatic intrusions or serpentinized peridotite. The relatively low V _p/V _s ratios of 1.75–1.78 modelled for the lower crust under the continental part of the Vøring Plateau are consistent with mafic intrusions mixed with blocks of stretched continental crust, but not with the presence of partially serpentinized peridotites. The lower crustal high-velocity body is restricted to the area of the Late Cretaceous/Early Tertiary rift that lead to continental break-up in Early Eocene. The same model can explain the observations in the northern Vøring Basin, but in the central and southern Vøring Basin the seismic velocities do not preclude a model involving serpentinized peridotite in addition to intrusions and continental remnants. On the west Iberia non-volcanic margin a similar layer is interpreted as serpentinized peridotite. The existence of Moho reflections, the observation of S-wave anisotropy but absence of P-wave anisotropy, uncertainties regarding supply of water to allow for significant serpentinization and very low stretching factors compared with the west Iberia Margin, are among factors that argue against the presence of serpentinized peridotite in the Vøring Basin.  相似文献   

VII-2 High efficiency energy conversion control for tide wave energy converter with pendulum     

Yasuhiko Dote  Kenji Yano 《Ocean Engineering》1985,12(6):594

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