Modelling seismic wave propagation in a two‐dimensional cylindrical whole‐earth model using the pseudospectral method     

Yanbin Wang  Hiroshi Takenaka  Takashi Furumura † 《Geophysical Journal International》2001,145(3):689-708

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The subsurface transport of heat and moisture and its effect on the environment: A numerical model   总被引：2，自引：0，他引：2  

Takashi Asaeda  Vu Thanh Ca 《Boundary-Layer Meteorology》1993,65(1-2):159-179

A numerical model was developed to study the transport of heat and vapor under the surface of bare soil and soil covered by some materials such as asphalt and concrete under no rainfall conditions. The computational results provide a good match with the experimental data. The results show that the transport of water vapor inside the soil has an important effect on the subsurface distribution of temperature, especially for bare soil. Because of evaporation, the temperature of bare soil is much lower than that under covered surfaces throughout the day and the temperature of the surface covered by asphalt is extremely high-higher than the atmospheric temperature even at night. An increase of thickness of the covering material further increases the temperature and heat stored under surfaces. The stored heat is released to the atmosphere at night, contributing to environmental effects such as the urban heat island.  相似文献   

Discovery of an ancient tsunami deposit in coastal sequences of southwest Japan: Verification of a large historic tsunami   总被引：1，自引：0，他引：1  

Koji  Minoura Takashi  Nakata 《Island Arc》1994,3(1):66-72

Abstract A tsunamigenic sand layer is present in coastal sequences of the Masuda Plain, southwest Japan. The radiometric age of the layer has been estimated at 930 ± 80 years BP. It is proposed that the deposit is the product of a large historic tsunami believed to have occurred in the Japan Sea on 16 June 1026 AD.  相似文献   

Spectroscopic Studies of the Solar Corona – V. Physical Properties of Coronal Structures     

Singh  Jagdev  Sakurai  Takashi  Ichimoto  Kiyoshi  Muneer  S. 《Solar physics》2003,212(2):343-359

Spectra around the 6374 Å [Fex] and 7892 Å [Fexi] emission lines were obtained simultaneously with the 25-cm coronagraph at Norikura Observatory covering an area of 200 ×500 of the solar corona. The line width, peak intensity and line-of-sight velocity for both the lines were computed using Gaussian fits to the observed line profiles at each location (4 ×4 ) of the observed coronal region. The line-width measurements show that in steady coronal structures the FWHM of the 6374 Å emission line increases with height above the limb with an average value of 1.02 mÅ arc sec^–1. The FWHM of the 7892 Å line also increases with height but at a smaller average value of 0.55 mÅ arc sec^–1. These observations agree well with our earlier results obtained from observations of the red, green, and infrared emission lines that variation of the FWHM of the coronal emission lines with height in steady coronal structures depends on plasma temperatures they represent. The FWHM gradient is negative for high-temperature emission lines, positive for relatively low-temperature lines and smaller for emission lines in the intermediate temperature range. Such a behaviour in the variation of the FWHM of coronal emission lines with height above the limb suggests that it may not always be possible to interpret an increase in the FWHM of emission line with height as an increase in the nonthermal velocity, and hence rules out the existence of waves in steady coronal structures.  相似文献   

Concentrations of Trace Elements in Carbonate Reference Materials Coral JCp-1 and Giant Clam JCt-1 by Inductively Coupled Plasma-Mass Spectrometry   总被引：1，自引：0，他引：1  

Mayuri Inoue  Masato Nohara  Takashi Okai  Atsushi Suzuki  Hodaka Kawahata 《Geostandards and Geoanalytical Research》2004,28(3):411-416

Trace elements in the Geological Survey of Japan carbonate reference materials Coral JCp-1 and Giant Clam JCt-1 were determined by inductively coupled plasma-mass spectrometry after digestion with 2% v/v HNO₃. A standard addition method was adopted in this determination in order to neutralise the Ca matrix effect. In addition, Sc, Y, In and Bi were used as internal standards to control the matrix effect and correct instrumental drift. Of the eighteen elements measured in JCp-1, precisions for fourteen elements, including Cu, Cd and Ba, were better than 10% RSD and concentrations ranged from 0.002 μg g^-1 (Cs) to 8.02 μg g^-1 (Ba). The concentrations of measured trace elements in JCt-1, except for Cu, were lower than those in JCp-1. Precisions for all elements with concentrations higher than 0.04 μg g^-1 in JCt-1 were also better than 10% RSD and concentrations were found to be between 0.001 μg g^-1 (Cs) and 4.84 μg g^-1 (Ba). The concentrations of more than fifteen trace elements in the aragonite reference materials are reported here for the first time. Both reference materials are suitable for use in geochemical studies of environmental reconstruction based upon biogenic carbonate materials.  相似文献   

Determination of Chlorine Contents in Geological Survey of Japan Reference Materials by Prompt Gamma Neutron Activation Analysis     

Takashi Sano  Takaaki Fukuoka  Toshiaki Hasenaka 《Geostandards and Geoanalytical Research》2004,28(3):443-448

We determined chlorine contents in nine GSJ (Geological Survey of Japan) reference materials (JB-1, 1a, 2, 3; JA-1, 2, 3; JR-1, 2) by prompt gamma neutron activation analysis, employing the standard addition method. Pressed powder disks of each reference material were used for neutron irradiation and gammaray measurement, after known quantities (25-200 μl) of sodium chloride solution were added. The influence of the nearby sodium peak overlap was checked, and fluctuations in the chlorine count rate were corrected using silicon as an internal standard. The slopes of calibration lines for seven reference materials (JB-1, 2, 3; JA-1, 2, 3; JR-2) and SiO₂ powders fall within 5% error, and their chlorine values were obtained from the intercepts. Chlorine contents in JB-1 a and JR-1 were also determined by using the calibration lines. Our chlorine values ranged from 26.1 to 934 μg g-¹, which agrees well with the previously reported values.  相似文献   

Deep structure of the Mozumi-Sukenobu fault, central Japan, estimated from the subsurface array observation of fault zone trapped waves   总被引：1，自引：0，他引：1  

Takashi Mizuno  Kin'ya Nishigami  Hisao Ito  Yasuto Kuwahara 《Geophysical Journal International》2004,159(2):622-642

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Connectivity of molten Fe alloy in peridotite based on in situ electrical conductivity measurements: implications for core formation in terrestrial planets   总被引：1，自引：0，他引：1  

Takashi Yoshino  Tomoo Katsura 《Earth and Planetary Science Letters》2004,222(2):625-643

The connectivity of molten Fe-S in peridotite has been experimentally investigated by means of in situ electrical conductivity measurements at high temperatures and 1 GPa. Starting materials were powdered mixtures of peridotite KLB-1 with various amounts (0, 3, 6, 13, 19, 24 vol.%) of the 1 GPa eutectic composition in the Fe-FeS binary system. At temperatures above the eutectic point in the Fe-FeS system (∼980 °C) and below the solidus of KLB1 (∼1200 °C), molten Fe-S in a solid silicate matrix interconnects when the volume fraction is over ∼5%. Conductivity-temperature paths indicate that in the presence of partial silicate melting the connectivity of molten Fe-S in a peridotite matrix is inhibited. Based on observations of retrieved samples, the percolation threshold of Fe-S melts in the presence of low to moderate degrees of silicate melt is estimated at 13±2 vol.%. These results indicate that if the volume fraction of Fe-alloy in a planetesimal was initially greater than 5%, and if early heating by decay of radionuclides raised the temperature of the interior above the Fe-alloy melting point, initial metal segregation was controlled by permeable flow of molten iron alloy in a solid silicate matrix. These conditions were likely met by many terrestrial objects in the early solar nebula. Efficient removal of residual Fe-alloy (5 vol.%) from silicate requires high-degree melting of silicate so that metal can segregate as droplets. Giant impacts during the final stage of accretion of large planetary objects could supply the energy required for high-degrees of melting. Alternatively, if initial metal segregation were delayed until a planetary object grew to large size (∼1000 km in diameter), release of gravitational potential energy due to metal segregation could contribute enough heat to form a magma ocean.  相似文献   

Determination of Ti, K, Sm and Gd Values in Geological Survey of Japan Reference Materials by Prompt Gamma Neutron Activation Analysis     

Takashi Sano  Toshiaki Hasenaka  Hiroyuki Sawahata  Takaaki Fukuoka 《Geostandards and Geoanalytical Research》2006,30(1):31-37

Prompt gamma neutron activation analysis was applied to the determination of the titanium, potassium, samarium and gadolinium contents of nine Geological Survey of Japan (GSJ) reference materials (JB-1, 1a, 2, 3; JA-1, 2, 3; JR-1, 2). Firstly, the values in JB-1 were determined by the standard addition method: pressed powder disks of JB-1 were used for neutron irradiation and gamma-ray measurements, after known quantities of standard reagents had been added. Secondly, the contents of eight other reference materials were determined by comparison methods using JB-1 as the comparative standard. The precision of analyses were obtained by replicate determinations on these samples. The relative standard deviation was generally less than 5%. For most samples, analysed values agreed well (< 5%) with the recommended values.  相似文献   

A k - *epsiv Turbulence Closure Model For The Atmospheric Boundary Layer Including Urban Canopy     

Vu Thanh Ca  Yasunobu Ashie  Takashi Asaeda 《Boundary-Layer Meteorology》2002,102(3):459-490

A numerical model for the computation of the wind field,air temperature and humidity in the atmospheric boundary layer (ABL) including the urbancanopy was developed for urban climate simulation. The governing equations of the modelare derived by applying ensemble and spatial averages to the Navier–Stokes equation, continuityequation and equations for heat and water vapour transfer in the air. With the spatial averagingprocedure, effects of buildings and other urban structures in the urban canopy can be accounted for byintroducing an effective volume function, defined as the ratio between the volume of air in acomputational mesh over the total volume of the mesh. The improved k - model accounts for the anisotropyof the turbulence field under density stratification. In the improved k - model, the transportof momentum and heat in the vertical direction under density stratification is evaluated based onthe assumption of a near-equilibrium shear flow where transport effects on the stresses andheat fluxes are negligible. The heating processes at surfaces of buildings and ground are alsomodelled. The comparison of the computational results obtained with the present modeland existing observational data and numerical models shows that the present model is capableof predicting the structure of turbulence in the urban canopy layer under density stratification.Numerical experiments with the new model show that the flow behaviour of the air in the urbancanopy layer is strongly affected by the existence of buildings and density stratification.  相似文献