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111.
Naoki Hirose 《Journal of Oceanography》2011,67(3):323-336
Significant impacts of the subgridscale parameterizations have been emphasized in modeling the ocean circulations, but various
different parameter values are applied to similar numerical studies often without any justification. This study objectively
estimates a set of empirical parameters along with their uncertainty for circulation modeling of the East Asian Marginal Seas.
The solutions for 14 major parameters are obtained by using model Green’s functions with constraints of climatological temperature
and salinity data. The largest cost function reduction occurs in the eastern Japan Sea associated with the sharp gradient
of the Polar Front. The calibrated parameters are also validated with realistic transport and path of the Kuroshio in the
final experiment. The inverse estimation shows that freshwater discharges from small rivers can be attributed to the coastal
precipitation over a strip of land 74–81 km wide. The thickness diffusion coefficient may be similar to the isopycnal and
horizontal diffusion coefficients in their magnitude. The accelerated initial condition also contributes to the cost function
reduction resulting in weaker trends of deep temperature. Most importantly, estimated scaling factors suggest a significant
reduction of the reanalyzed wind stress data for more realistic ocean circulations. Possible reasons for the momentum missing
are also discussed. 相似文献
112.
113.
Kiyoaki?WajimaEmail author Kenta?Fujisawa Masaaki?Hayashida Naoki?Isobe 《Journal of Astrophysics and Astronomy》2014,35(3):215-218
We made simultaneous single-dish and VLBI observations of a gamma-ray narrow-line Seyfert 1 (NLS1) galaxy 1H 0323+342. We found significant flux variation at 8 GHz on a time scale of one month. The total flux density varied by 5.5% in 32 days, corresponding to a variability brightness temperature of 7.0 × 1011 K. We also obtained brightness temperatures of greater than 5.2 × 1010 K from the VLBI images. These high brightness temperatures suggest that the source has nonthermal processes in the central engine. The source structure could be modelled by two elliptical Gaussian components on the parsec scales. The flux of the central component decreases in the same way as the total flux density, showing that the short-term variability is mainly associated with this component. 相似文献
114.
Naoki Kabeya Masanori Katsuyama Masatoshi Kawasaki Nobuhito Ohte Atsuko Sugimoto 《水文研究》2007,21(3):308-322
We measured deuterium excess (d = δD ? 8δ18O) in throughfall, groundwater, soil water, spring water, and stream water for 3 years in a small headwater catchment (Matsuzawa, 0·68 ha) in the Kiryu Experimental Watershed in Japan. The d value represents a kinetic effect produced when water evaporates. The d value of the throughfall showed a sinusoidal change (amplitude: 6·9‰ relative to Vienna standard mean ocean water (V‐SMOW)) derived from seasonal changes in the source of water vapour. The amplitude of this sinusoidal change was attenuated to 1·3–6·9‰ V‐SMOW in soil water, groundwater, spring water, and stream water. It is thought that these attenuations derive from hydrodynamic transport processes in the subsurface and mixing processes at an outflow point (stream or spring) or a well. The mean residence time (MRT) of water was estimated from d value variations using an exponential‐piston flow model and a dispersion model. MRTs for soil water were 0–5 months and were not necessarily proportional to the depth. This may imply the existence of bypass flow in the soil. Groundwater in the hillslope zone had short residence times, similar to those of the soil water. For groundwater in the saturated zone near the spring outflow point, the MRTs differed between shallow and deeper groundwater; shallow groundwater had a shorter residence time (5–8 months) than deeper groundwater (more than 9 months). The MRT of stream water (8–9 months) was between that of shallow groundwater near the spring and deeper groundwater near the spring. The seasonal variation in the d value of precipitation arises from changes in isotopic water vapour composition associated with seasonal activity of the Asian monsoon mechanism. The d value is probably an effective tracer for estimating the MRT of subsurface water not only in Japan, but also in other East Asian countries influenced by the Asian monsoon. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
115.
116.
Massimo Meneghetti Naoki Yoshida Matthias Bartelmann Lauro Moscardini Volker Springel Giuseppe Tormen Simon D. M. White 《Monthly notices of the Royal Astronomical Society》2001,325(1):435-442
We carry out ray tracing through five high-resolution simulations of a galaxy cluster, to study how its ability to produce giant gravitationally lensed arcs is influenced by the collision cross-section of its dark matter. In three cases typical dark matter particles in the cluster core undergo between 1 and 100 collisions per Hubble time; two more explore the long ('collisionless') and short ('fluid') mean free path limits. We study the size and shape distributions of arcs and compute the cross-section for producing 'extreme' arcs of various sizes. Even a few collisions per particle modifies the core structure enough to destroy the ability of the cluster to produce long, thin arcs. For larger collision frequencies the cluster must be scaled up to unrealistically large masses before it regains the ability to produce giant arcs. None of our models with self-interacting dark matter (except the 'fluid' limit) is able to produce radial arcs; even the case with the smallest scattering cross-section must be scaled to the upper limit of observed cluster masses before it produces radial arcs. Apparently the elastic collision cross-section of dark matter in clusters must be very small, below 0.1 cm2 g−1 , to be compatible with the observed ability of clusters to produce both radial arcs and giant arcs. 相似文献
117.
Midori Tokutani Naoki Yoshida S. Peng Oh Naoshi Sugiyama 《Monthly notices of the Royal Astronomical Society》2009,395(2):777-780
We calculate the spin temperature and 21-cm brightness of early H ii regions around the first stars. We use outputs from cosmological radiation-hydrodynamics simulations of the formation and evolution of early H ii regions. In the pre-re-ionization era, H ii regions around massive primordial stars have diameters of a few kpc. The gas within the H ii regions is almost fully ionized, but begins recombining after the central stars die off. The relic H ii regions are then seen as bright emission sources in hydrogen 21 cm. We make brightness temperature maps of the H ii regions, accounting for radiative coupling with Lyman α photons in a simplified manner. The spin temperature in the relic H ii region is close to the gas kinetic temperature, generally several hundred to several thousand degrees. We show that the relic H ii region can be as bright as δ T b ∼ 100 mK in differential temperature against the cosmic microwave background for an angular resolution of subarcseconds. While individual early H ii patches will not be identified by currently planned radio telescopes, the collective fluctuations from early H ii regions might imprint signatures in the 21-cm background. 相似文献
118.
A fundamental mechanism on the atomic level for self-diffusion in the proton layer of portlandite, Ca(OH)2, was investigated by conducting hydrogen–deuterium (H–D) exchange diffusion experiments and by deriving potential energy
curves of OH vibrations from optical absorption measurements. Synthetic single crystals of portlandite were used in H–D experiments
between 250 and 450°C at 150 MPa. Arrhenius parameters for proton diffusion perpendicular to the c-axis gave a frequency factor of 1.0 × 10−10 m2/s and activation energy of 0.61 eV (58.5 kJ/mol). The activation energy corresponds to the height of the potential barrier
between two oxygen atoms across an interlayer. The potential barrier height was also theoretically estimated using the OH
potential energy curve (OH-PEC) determined by optical absorption measurements. Experimental and theoretical results suggest
that the potential barrier height cannot be simply determined by overlapping two OH-PECs. The potential barrier derived theoretically
was 3.11 eV. This is too high for the activation energy of the proton diffusion. It implies that the interaction between a
diffusing proton and the vacancy of a proton site, and the shortening of interlayer oxygen distance by thermal vibration reduce
the potential barrier. 相似文献
119.
Abstract Tectonic episodes in a sedimentary basin are described on the basis of an integrated study combining reflection seismic interpretation, drilling survey and paleomagnetism. A shallow inclined borehole penetrated a fault shown by reflection seismic and geological surveys in the Mizunami area, in the eastern part of southwest Japan. Paleomagnetic measurements were carried out on core samples successfully oriented using side-wall image logging of structural attitude. At six horizons, stable characteristic remanent magnetization (ChRM) was confirmed through thermal and alternating field demagnetization tests, which were carried by magnetite with minor amounts of high coercivity minerals, as revealed by experiments of stepwise acquisition of isothermal remanent magnetization. After correction of multiphase deformation inferred from borehole structural analysis, ChRM directions were combined with previous data and confirmed an easterly deflection reflecting the coherent clockwise rotation of the arc before the Middle Miocene. Compilation of reliable paleomagnetic data described differential rotation of the eastern part of southwest Japan raised by collision of the Izu–Bonin Arc since the Middle Miocene. The present study suggests that (i) the Mizunami area is adjacent to a highly deformed zone bounded by the Akaishi Tectonic Line (ATL), and (ii) forearc deformation of southwest Japan is localized around the ATL, which is quite different from gradual bending on the back-arc side without remarkable crustal break related to the collision event. 相似文献
120.