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排序方式: 共有69条查询结果,搜索用时 15 毫秒
21.
A dataset of continental river discharge based on JRA-55 for use in a global ocean circulation model
Tatsuo Suzuki Dai Yamazaki Hiroyuki Tsujino Yoshiki Komuro Hideyuki Nakano Shogo Urakawa 《Journal of Oceanography》2018,74(4):421-429
A dataset of historical river discharge into oceans was created using the CaMa-Flood global river routing model and adjusted runoff from the land component of JRA-55. The major rivers were well resolved with a 0.25° horizontal resolution. The total runoff on each drainage basin exhibits a distinctive bias on decadal time scales. The input runoff data were modified using 5-year low-pass-filtered multiplicative factors to fit the annual mean climatology and decadal variations in the reference dataset. The model incorporated data from 1958 to 2016. The yearly and seasonal variations of the major rivers are well represented by the model. 相似文献
22.
Hisashi Asanuma Yusuke Sawaki Shuhei Sakata Hideyuki Obayashi Kazue Suzuki Kouki Kitajima Takafumi Hirata Shigenori Maruyama 《Island Arc》2018,27(4)
Supracrustal rocks around the North Pole Dome area, Western Australia, provide valuable information regarding early records of the evolution of crustal processes, surface environments, and biosphere. Owing to the occurrence of the oldest known microfossils, the successions at the North Pole Dome area have attracted interest from many researchers. The Paleoarchean successions (Warrawoona Group) mainly comprise mafic‐ultramafic greenstones with intercalated cherts and felsic lavas. Age constraints on the sediments have been mainly based on zircon U–Pb geochronology. However, many zircon grains have suffered from metamictization and contain anomalously high contents of common Pb, which makes interpretation of the U–Pb data complicated. In order to provide more convincing chronological constraints, an U–Pb Concordia age is widely accepted as the best estimate. Most zircons separated from two adamellites also suffered from severe metamictization. In our analyses, less metamictized domains were selected using a pre‐ablation technique in conjunction with elemental mapping, and then their U–Pb isotopic compositions were determined with a laser ablation inductively coupled plasma mass spectrometry. Most analyzed domains contained certain amounts of common Pb (204Pb/206Pb > 0.000 1), whereas three and five U–Pb data points with less common Pb (204Pb/206Pb < 0.000 1) were obtained. These U–Pb datasets yielded U–Pb Concordia ages of ca 3 445 Ma and 3 454 Ma, respectively. These ages represent the timing of the adamellite intrusion, and constrain the minimum depositional age of the Warrawoona Group. In addition, a single xenocrystic zircon grain showed a 207Pb/206Pb age of ca 3 545 Ma, supporting the idea that the sialic basement of the Pilbara Craton existed prior to 3 500 Ma. The in situ U–Pb zircon dating combined with the pre‐ablation technique has the potentials to identify non‐metamictized parts and to yield precise and accurate geochronological data even from partially metamictized zircons. 相似文献
23.
Hideyuki Kawamura Toshimichi Ito Naoki Hirose Tetsutaro Takikawa Jong-Hwan Yoon 《Journal of Oceanography》2009,65(4):439-454
The branches of the Tsushima Warm Current (TWC) are realistically reproduced using a three-dimensional ocean general circulation
model (OGCM). Simulated structures of the First Branch and the Second Branch of the TWC (FBTWC and SBTWC) in the eastern Japan
Sea are mainly addressed in this study, being compared with measurement in the period September–October 2000. This is the
first numerical experiment so far in which the OGCM is laterally exerted by real volume transports measured by acoustic Doppler
current profiler (ADCP) through the Tsushima Straits and the Tsugaru Strait. In addition, sea level variation measured by
tide-stations along the Japanese coast as well as satellite altimeters is assimilated into the OGCM through a sequential data
assimilation method. It is demonstrated that the assimilation of sea level variation at the coastal tide-stations is useful
in reproducing oceanic conditions in the nearshore region. We also examine the seasonal variation of the branches of the TWC
in the eastern Japan Sea in 2000. It is suggested as a consequence that the FBTWC is continuous along northwestern Honshu
Island in summertime, while it degenerates along the coast between the Sado Strait and the Oga Peninsula in other seasons.
On the other hand, a mainstream of the SBTWC exists with meanders and eddies in the offshore region deeper than 1000 m to
the north of the Sado Island throughout the year. 相似文献
24.
The mechanism governing the mean state and the seasonal variation of the transports through the straits of the Japan Sea is
studied using a newly presented, simple analytical model and a basin scale general circulation model (GCM). The GCM reproduces
the transports through the straits of the Japan Sea realistically owing to its fine horizontal resolution of about 20 km and
realistic topography. A series of experiments conducted by changing surface forcing shows that the annual mean wind-driven
circulation in the North Pacific Ocean is most responsible for the formation of the mean transports. It is also found that
the seasonal variation of the alongshore component of monsoonal wind stress over the North Pacific basin, especially that
over the Okhotsk Sea, is responsible for the seasonal variation of the transports. The simple analytical model can explain
these simulated features very well. The physical concept of this model is based on the formation of the around-island circulation
through the adjustment of coastally trapped waves and Rossby waves and geostrophic control at the narrow straits. It solves
the sea surface heights (SSHs) at the edge of each strait and the transport through it. The value of the line integral of
the SSH along the island is determined by the baroclinic Rossby waves approaching the island from the east and the alongshore
wind stress around the island. The basin scale seasonal variation of SSH along the coast induced by the variation of the alongshore
monsoonal wind stress can also be incorporated into this model by giving the SSH anomaly at the northeastern point of the
Soya Strait. Thus, it is suggested that both the mean state and the seasonal variation are caused mainly by wind stress forcing.
Minor modification by the seasonal heat flux forcing brings the amplitude and the phase of the seasonal variation closer to
the observed values. 相似文献
25.
Hideyuki Kamaya 《Astrophysics and Space Science》1997,253(2):199-204
The author proposes the possibility to observe the HI column density oscillation in small scales (∼ AU-scale). If such variance
of the column density were to be observed, he would suggest that the observational results show the existence of some type
of waves in two-phase gas mixture. Such wave is known to be a void wave in the context of multi-phase fluid dynamics. If the
variation of HI column density is representation of the void wave, we can also expect the HII density variations have anti-correlation
to the HI density fluctuations, in the context of classical two phase model of interstellar medium.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
26.
27.
Hideyuki Saio C. Simon Jeffery 《Monthly notices of the Royal Astronomical Society》2002,333(1):121-132
We have examined the evolution of merged low-mass double white dwarfs that become luminous helium stars. We have approximated the merging process by the rapid accretion of matter, consisting mostly of helium, on to a carbon–oxygen (CO) white dwarf. After a certain mass is accumulated, a helium shell flash occurs, the radius and luminosity increase and the star becomes a yellow giant. Mass accretion is stopped artificially when the total mass reaches a pre-determined value. When the mass above the helium-burning shell becomes small enough, the star evolves blueward almost horizontally in the Hertzsprung–Russell diagram. The theoretical models for the merger of a 0.6-M⊙ CO white dwarf with a 0.3-M⊙ He white dwarf agree very well with the observed locations of extreme helium stars in the log T eff –log g diagram, with their observed rates of blueward evolution, and with luminosities and masses obtained from their pulsations. Together with predicted merger rates for CO+He white dwarf pairs, the evolutionary time-scales are roughly consistent with the observed numbers of extreme helium stars. Predicted surface carbon and oxygen abundances can be consistent with the observed values if carbon and oxygen produced in the helium shell during a previous asymptotic giant branch phase are assumed to exist in the helium zone of the initial CO white dwarfs. These results establish the CO+He white dwarf merger as the best, if not only, viable model for the creation of extreme helium stars and, by association, the majority of R Coronae Borealis stars. 相似文献
28.
Vinicius Aguiar de Souza Levent Kirkayak Katsuyuki Suzuki Hideyuki Ando Hidetoshi Sueoka 《Ocean Engineering》2012
This paper describes an approach to simulate a seven-tier stack consisting of scaled model of a 20 ft ISO freight container and its linking connectors, denominated twist locks, subjected to dynamical load induced by its base. The physical (dimensions, mass, and moments of inertia) and structural (longitudinal, transversal and torsional stiffness) characteristics of the scaled models were decided based on two dimensionless numbers: ratios between gravity force and inertia force, and elastic force divided by inertia force, through experimental and numerical analysis. A series of experiments with controlled parameters were performed using a shaking table test to understand the effects of each variable in the container stack dynamics and present enough data to validate the numerical model. The results of this study indicate that the numerical model built is a promising tool for further study. Moreover, the model is able to predict conditions close to real situations faced by container stacks while storage on a ship's deck. 相似文献
29.
Abstract Ocean bottom bases (OBBs) have been installed on both sides of the axis of the Sagami Trough east of the Izu Peninsula, central Japan, as the first step toward long‐term geodetic and geophysical observations at the plate boundary (subduction zone). The OBB is a platform for seafloor measurements; otherwise it is difficult to find an appropriate place for precise seafloor measurements in the subduction zones. It is made of a nonmagnetic concrete block of size 1100 × 1100 × 500 mm. It was lowered from a ship using a winch wire and installed on a predetermined place with its position being monitored by an acoustic transponder system and a 30‐kHz bottom pinger with an accuracy of about 2 m. It was confirmed later during the divings on board the submersible Shinkai 2000 that the OBB was installed on a flat mud bottom in normal condition. No change has been recognized in the installation condition in 3 years; the OBB is stable enough to be used for acoustic range measurements on the seafloor as well as for several geophysical measurements. The resolution of seafloor range measurement can be improved by two orders by using phase measurement techniques with the aid of pulse compression. Precise acoustic range measurement of the order of 10?5 is feasible under the following conditions: two‐way measurements between the two OBBs installed on the slope facing each other with angles larger than 1.5°. Correction is necessary for the effect of long‐term temperature variation. 相似文献
30.
Alfred Gautschy Hideyuki Saio & Housi Harzenmoser 《Monthly notices of the Royal Astronomical Society》1998,301(1):31-41
Rapidly oscillating Ap stars constitute a unique class of pulsators with which to study non-radial oscillations under some — even for stars — unusual physical conditions. These stars are chemically peculiar, they have strong magnetic fields and they often pulsate in several high-order acoustic modes simultaneously. We discuss here an excitation mechanism for short-period oscillation modes based on the classical κ mechanism. We particularly stress the conditions that must be fulfilled for successful driving. Specifically, we discuss the roles of the chemical peculiarity and strong magnetic field on the oscillation modes and what separates these pulsators from δ Scuti and Am-type stars. 相似文献