Variations in the redox state of As and Fe measured by X-ray absorption spectroscopy in aquifers of Bangladesh and their effect on As adsorption     

Takaaki Itai  Yoshio Takahashi  Ashraf Ali Seddique  Teruyuki Maruoka  Muneki Mitamura 《Applied Geochemistry》2010

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Determination of the oxidation state of radiogenic Pb in natural zircon using X-ray absorption near-edge structure     

Kazuya Tanaka  Yoshio Takahashi  Kenji Horie  Hiroshi Shimizu  Takashi Murakami 《Physics and Chemistry of Minerals》2010,37(4):249-254

We examined the L_III-edge Pb X-ray absorption near-edge structure (XANES) of three natural zircon samples with different amounts of radiation doses (1.9 × 10¹⁵ to 6.8 × 10¹⁵ α-decay events/mg). The results suggest that the oxidation state of radiogenic Pb in the zircon sample with the highest radiation dose is divalent. The XANES spectra of the two other samples with lower radiation doses suggest that radiogenic Pb(II) is present, and further that some Pb may be tetravalent. This is the first work on the determination of the oxidation state of radiogenic Pb in natural zircon using XANES.  相似文献   

Potential of low cost close‐range photogrammetry system in soil microtopography quantification     

Mohamed A. M. Abd Elbasit  Hisao Anyoji  Hiroshi Yasuda  Shunichi Yamamoto 《水文研究》2009,23(10):1408-1417

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Field Survey of the 1996 Irian Jaya Earthquake Tsunami in Biak Island     

Matsutomi  H.  Shuto  N.  Imamura  F.  Takahashi  T. 《Natural Hazards》2001,24(3):199-212

Runup data in Biak Island and itsnearby islets are described with discussions oftsunami magnitude and a few characteristics such aswitnessed arrival times, wave periods and wavenumbers. From an engineering viewpoint, a relationbetween inundation depth and current velocity on landis also described with relations between inundationdepth and degree of damage to houses and between sanderosion depth and current velocity in backshoreregion, based on data collected from the present andpast tsunamis.  相似文献   

Explaining Access to Human Services: The Influence of Descriptive and Behavioral Variables     

Lois M. Takahashi  Gayla Smutny 《The Professional geographer》2001,53(1):12-31

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Numerical simulation of the 1992 Flores tsunami: Interpretation of tsunami phenomena in northeastern Flores Island and damage at Babi Island   总被引：2，自引：0，他引：2  

Fumihiko Imamura  Edison Gica  Tomoyuki Takahashi  Nobuo Shuto 《Pure and Applied Geophysics》1995,144(3-4):555-568

Numerical analysis of the 1992 Flores Island, Indonesia earthquake tsunami is carried out with the composite fault model consisting of two different slip values. Computed results show good agreement with the measured runup heights in the northeastern part of Flores Island, except for those in the southern shore of Hading Bay and at Riangkroko. The landslides in the southern part of Hading Bay could generate local tsunamis of more than 10 m. The circular-arc slip model proposed in this study for wave generation due to landslides shows better results than the subsidence model, It is, however, difficult to reproduce the tsunami runup height of 26.2 m at Riangkroko, which was extraordinarily high compared to other places. The wave propagation process on a sea bottom with a steep slope, as well as landslides, may be the cause of the amplification of tsunami at Riangkroko. The simulation model demonstrates that the reflected wave along the northeastern shore of Flores Island, accompanying a high hydraulic pressure, could be the main cause of severe damage in the southern coast of Babi Island.  相似文献   

Seismic response controlled structure with Active Variable Stiffness system     

Takuji Kobori  Motoichi Takahashi  Tadashi Nasu  Naoki Niwa  Katsura Ogasawara 《地震工程与结构动力学》1993,22(11):925-941

The Active Variable Stiffness (AVS) system is proposed as a seismic response control system. It actively controls structural characteristics, such as stiffness of a building, to establish a non-resonant state against earthquake excitations, thus suppressing the building's response. It consumes a relatively small amount of energy and maintains the safety of the building in moderate to severe earthquakes. In order to accumulate practical data and investigate them, a building has been constructed as a trial. This paper describes the applied system, the control algorithm, verification of stiffness selection, results of tests for verifying system characteristics, some observed earthquake records and simulation analyses. Responses in controlled and uncontrolled states have been compared to show the effectiveness of the proposed system.  相似文献   

An evaluation of the apparent dissociation constants of carbonic acid in seawater     

Taro Takahashi  Peter Kaiteris  Wallace S. Broecker  Arnold E. Bainbridge 《Earth and Planetary Science Letters》1976,32(2):458-467

The internal consistency of five sets of apparent dissociation constants of carbonic acid in seawater obtained by Buch (1951), Lyman (1956), Edmond and Gieskes (1970), Hansson (1973) and Mehrbach et al. (1973) have been tested using the GEOSECS Atlantic data for the total alkalinity, the total CO₂ concentration and the partial pressure of CO₂. As a measure of the consistency for each of the five sets of the dissociation constants with the data, the 77 measured values of the partial pressure of CO₂ have been compared with those calculated from the alkalinity and total CO₂ values determined for these samples. It has been found that: (1) the apparent dissociation constants of Lyman (1956), Hansson (1973) and Mehrbach et al. (1973) appear to be internally consistent with the data, whereas those of Buch (1951) and of Edmond and Gieskes (1970) appear to be markedly inconsistent with the GEOSECS data; and (2) on the basis of a statistical analysis of the data grouped in three temperature ranges, the dissociation constants of Lyman (1956) and of Mehrbach et al. (1973) appear to be most satisfactory.  相似文献   

Thermal history of iherzolite xenoliths—I. Petrology of iherzolite xenoliths from the ichinomegata crater,oga peninsula,northeast Japan     

Eiichi Takahashi 《Geochimica et cosmochimica acta》1980,44(11):1643-1658

The thermal history of four spinel lherzolites (Lhz-13. Lhz-28, Lhz-29 and Lhz-53) from tuff breccia of the Ichinomegata crater, northeast Japan, has been studied in detail. Lhz-13 and Lhz-53 showed nearly perfect chemical homogeneity of the constituent minerals, and increase of Ca near the rim of olivine is the only disequilibrium evidence observed. In addition to the Ca zoning in olivine, Lhz-28 and Lhz-29 revealed compositional zoning in the Mg/Mg + Fe ratio and Ca content in ortho- and clinopyroxenes. Lhz-13 and Lhz-53 equilibrated at about 800°C in the upper mantle, based on Fe/Mg partitioning between olivine/spinel and olivine/clinopyroxene, and on the mutual solubility of Ca between olivine and pyroxenes. Lhz-28 and Lhz-29 also equilibrated originally at about 800°C, but were preheated at about 1000°C prior to their entrapment by the ascending host magma. The Fe/Mg partitioning between olivine /spinel and olivine/clinopyroxene reequilibrated during the preheating event: however, the Ca solubility did not reequilibrate. Olivine alone has rehomogenized with a high-Ca content but pyroxenes were compositionally zoned with Ca. The preheating event, indicated by the high-Ca content in the core of olivine, is recognized from about a half of the Ichinomegata Iherzolites (50 xenoliths were studied).The duration of heating during the transport of the xenolith by the magma (estimated from the width of the Ca zoning in the rim of olivine) ranges between several hours to a year depending on the rock specimen. From the requirement to reset olivine core compositions, the duration of the preheating event was estimated as greater than 1000 yr.  相似文献   

Isotopic anomalies of noble gases in meteorites and their origins—VII. C3V carbonaceous chondrites     

Jun-Ichi Matsuda  Roy S. Lewis  Hiroshi Takahashi  Edward Anders 《Geochimica et cosmochimica acta》1980,44(11):1861-1874

Noble gases were measured in bulk samples of the C3V chondrites Grosnaja, Vigarano, and Leoville, and in HF,HCl-insoluble residues before and after etching with HNO₃. The residues were characterized by INAA and SEM. Gas components were determined, directly or by subtraction, for the following fractions: HF,HCl-solubles (?98% of the meteorite), ‘sphase Q’, a poorly characterized trace mineral that is insoluble in HCl-HF but soluble in HNO₃, and an insoluble residue, consisting of ferrichromite, carbonaceous matter, and spinel.Bulk meteorites show some correlation of the noble-gas pattern with McSween's subclasses: two ‘oxidized’ C3V's—Allende (LEWIS et al, 1975) and Grosnaja— have lower Ar/Xe but higher Ne/Xe ratios than the ‘reduced’ C3V's—Vigarano and Leoville—which are transitional to LL3's and C3O chondrites in both respects. An HCl-soluble mineral of high Ar/Xr ratio seems to be responsible. In other respects, the 3 C3V's of this study resemble Allende, with only moderate differences. Phase Q contains most of the Ar, Kr, Xe, but only small amounts of Ne; the etched residues contain planetary Ne ($\text{Ne}{}^{20}\text{Ne}{}^{22}\text{? 8.5}$) and the controversial CCFXe component, enriched in the heavy Xe isotopes ($\text{Xe136}\text{Xe132 ? 0.4–0.5}$). The CCFXe is accompanied by an ‘L-Xe’ component that is enriched in the light Xe isotopes. The proportion of the two is virtually constant in C3V's. as in all other C-chondrites. in contrast to the ~ 2-fold variation in ordinary chondrites.C3V's have systematically higher $\text{Xe}{}^{136}\text{Xe}{}^{132}$ ratios, and hence higher ratios of CCFXe to planetary Xe, than do other chondrite classes. This may reflect some peculiarity in their formation conditions, favoring uptake of CCFXe.  相似文献