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91.
We measured the electrical resistivity of face-centered-cubic (fcc) structured iron hydrides at high pressures up to 65 GPa and high temperatures in a laser-heated diamond anvil cell. The results indicate that the resistivity of stoichiometric fcc FeHx (x ~ 1.0) is smaller than that of fcc Fe at the same pressure and temperature conditions. The same behavior was also observed in fcc FeNiHx (x ~ 1.0). On the other hand, hydrogen-poor fcc FeHx (x < 0.77) showed a resistivity comparable to that of the fcc phase of pure iron. Therefore, we conclude that the stoichiometric fcc Fe (–Ni) hydride is more conductive than Fe (–Ni) with the same crystal symmetry, and the impurity resistivity of hydrogen in Fe is vanishingly small. Even if hydrogen is the major light element in the Earth's core, it would have little influence on the electrical and thermal conductivity of Fe–Ni alloys, and hence the thermal evolution of the core. 相似文献
92.
Akira Hasegawa Kenji Ohta Takashi Yagi Kei Hirose Yoshiyuki Okuda Tadashi Kondo 《Comptes Rendus Geoscience》2019,351(2-3):229-235
We measured the lattice thermal conductivities of Fe0.98O wüstite and iron-rich (Mg,Fe)O magnesiowüstite using the pulsed light heating thermoreflectance technique with a diamond anvil cell up to 61 GPa at 300 K. We found that the thermal conductivity of wüstite does not show a monotonic increase as a function of pressure, contrary to that of MgO periclase. Rocksalt (B1) to rhombohedral B1 transition is likely to induce an abnormal pressure response in the conductivity of wüstite. Our results also show that magnesiowüstite has a lower conductivity than that of MgO and FeO endmembers due to a strong iron impurity effect, which is well reproduced by a model considering phonon-impurity scattering in a binary solid solution. 相似文献
93.
Bao‐Lin Xue Zhanling Li Xin‐An Yin Tieliang Zhang Shin'ichi Iida Kyoichi Otsuki Takeshi Ohta Qinghua Guo 《水文研究》2015,29(6):1017-1026
A larch forest in eastern Siberia was characterized by the presence of two distinct storeys, the overstorey with a small leaf area index (LAI) and a dense understorey with a relatively large LAI. To understand the roles of the overstorey and understorey in forest–atmosphere water exchange, canopy conductance (Gc), a critical parameter used in determining the energy and mass exchange, was calculated on the basis of latent heat flux above the overstorey and understorey, measured separately. Results showed that Gc for the overstorey (Gco) and understorey (Gcu) experienced different seasonal fluctuations. Gco was smaller than Gcu during periods of leaf expansion and leaf fall and showed an increasing trend until 1 month after the onset of leaf expansion. In contrast, a sharp decrease in Gco was observed immediately before onset of leaf fall. Furthermore, Gco was slightly larger than Gcu during the fully foliated period. A simple model using solar radiation and vapour pressure deficit (D) as inputs successfully reproduced the Gc in fully foliated periods with acceptable accuracy. Furthermore, both the understorey and overstorey in this study have a large reference Gc (Gc at D = 1 KPa) than their counterparts of other boreal forests and would not be able to sustain a constant leaf–soil water potential difference as D increases. We speculated that this confers the forest with an advantage allowing it to be able to sustain carbon assimilation during large D days and thus provides for the survival of the ecosystem during the short growing season at this site. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
94.
Daisuke Inazu Tadahiro Sato Satoshi Miura Yusaku Ohta Kazuyuki Nakamura Hiromi Fujimoto Christopher F. Larsen Tomoyuki Higuchi 《Journal of Oceanography》2009,65(3):335-347
An accurate prediction of ocean tides in southeast Alaska is developed using a regional, barotropic ocean model with a finite
difference scheme. The model skill is verified by the observational tidal harmonics in southeast Alaska including Glacier
Bay. The result is particularly improved in Glacier Bay compared to the previous model described by Foreman et al. (2000). The model bathymetry dominates the model skill. We re-estimate tidal energy dissipation in the Alaska Panhandle
and suggest a value for tidal energy dissipation of 3.4 GW associated with the M2 constituent which is 1.5 times the estimation of Foreman et al. (2000). A large portion of the M2 energy budget entering through Chatham Strait is dissipated in the vicinity of Glacier Bay. Moreover, it is shown that the
developed model has the potential to correct the ocean tide loading effect in geodetic data more efficiently than the model
of Foreman et al. (2000), especially around Glacier Bay. 相似文献
95.
Setsuya Nakada Hiroshi Shimizu Kazuya Ohta 《Journal of Volcanology and Geothermal Research》1999,89(1-4)
Following 198 years of dormancy, a small phreatic eruption started at the summit of Unzen Volcano (Mt. Fugen) in November 1990. A swarm of volcano-tectonic (VT) earthquakes had begun below the western flank of the volcano a year before this eruption, and isolated tremor occurred below the summit shortly before it. The focus of VT events had migrated eastward to the summit and became shallower. Following a period of phreatic activity, phreatomagmatic eruptions began in February 1991, became larger with time, and developed into a dacite dome eruption in May 1991 that lasted approximately 4 years. The emergence of the dome followed inflation, demagnetization and a swarm of high-frequency (HF) earthquakes in the crater area. After the dome appeared, activity of the VT earthquakes and the summit HF events was replaced largely by low-frequency (LF) earthquakes. Magma was discharged nearly continuously through the period of dome growth, and the rate decreased roughly with time. The lava dome grew in an unstable form on the shoulder of Mt. Fugen, with repeating partial collapses. The growth was exogenous when the lava effusion rate was high, and endogenous when low. A total of 13 lobes grew as a result of exogenous growth. Vigorous swarms of LF earthquakes occurred just prior to each lobe extrusion. Endogenous growth was accompanied by strong deformation of the crater floor and HF and LF earthquakes. By repeated exogenous and endogenous growth, a large dome was formed over the crater. Pyroclastic flows frequently descended to the northeast, east, and southeast, and their deposits extensively covered the eastern slope and flank of Mt. Fugen. Major pyroclastic flows took place when the lava effusion rate was high. Small vulcanian explosions were limited in the initial stage of dome growth. One of them occurred following collapse of the dome. The total volume of magma erupted was 2.1×108 m3 (dense-rock-equivalent); about a half of this volume remained as a lava dome at the summit (1.2 km long, 0.8 km wide and 230–540 m high). The eruption finished with extrusion of a spine at the endogenous dome top. Several monitoring results convinced us that the eruption had come to an end: the minimal levels of both seismicity and rockfalls, no discharge of magma, the minimal SO2 flux, and cessation of subsidence of the western flank of the volcano. The dome started slow deformation and cooling after the halt of magma effusion in February 1995. 相似文献
96.
97.
Michinori Honda Shintaro Ohno Atsushi Iizuka Katsuyuki Kawai Hideki Ohta 《Geotechnical and Geological Engineering》2011,29(2):171-180
An evaluation method for the mechanical behavior of unsaturated soils is studied in this paper. Although the mechanical behavior
of unsaturated soils is complicated, a simple modeling is preferable in practice. This is because the soil properties are
not homogeneous and ground data is limited when structures are being designed. In addition, in order to evaluate the reliability
of the design, the physical meanings of the parameters applied in the prediction model should be clear. Firstly, the authors
study the relationship between compaction curves and compression indexes in the unsaturated state that is used in the proposed
constitutive model. Based on the constitutive model, the stress paths for constant volume shear tests are formulated under
a constant void ratio condition and the stress paths for undrained shear tests are calculated under a constant water content
condition. In the case of unsaturated specimens, the volume of these specimens changes with the shear deformation and the
stress paths depend on the initial degree of saturation. The results of the calculation qualitatively describe the test results
by considering the changes in effective confining pressure in the undrained condition and the water retention curves. 相似文献
98.
Yasunori Mahara Tomoko Ohta Tomochika Tokunaga Hiroyuki Matsuzaki Eiji Nakata Yuki Miyamoto Yukihiro Mizuochi Toshiharu Tashiro Masahiro Ono Toshifumi Igarashi Keisuke Nagao 《Applied Geochemistry》2012
Fifty-three samples, including brines associated with oil and natural gas reservoirs and groundwater samples from deep boreholes, were collected from the Pacific and Japan Sea coastal regions in Japan. The 129I/127I and 36Cl/Cl ratios, and stable isotopes (δD and δ18O) are compared to investigate differences related to the geotectonic settings of the two regions. The δD and δ18O data indicate that brine and groundwater from the Pacific coastal region reflect mixing of meteoric water with connate seawater in the pores of sedimentary rocks. On the other hand, brine and groundwater from the Japan Sea coastal region have been hydrothermally altered. In particular, brines associated with petroleum accumulations at Niigata and Akita showed the same isotopic characteristics as fluids found in the Kuroko deposits of the Green Tuff region in northeastern Japan. There is little difference in the 36Cl/Cl ratios in brine and groundwater from the Pacific and Japan Sea coasts. Most brine and some deep groundwater, except those from the Pleistocene Kazusa Group, have already reached the average secular equilibrium ratio of 9.9 ± 2.7 × 10−15 for their mudstone and sandstone reservoirs. There was no correlation between the 36Cl/Cl ratios and differences in geotectonic setting between the Pacific and the Japan Sea coast. The molar I/Br ratio suggests that the I in all of water samples was of biogenic origin. The average 129I/127I ratio was 290 ± 130 × 10−15 to 294 ± 105 × 10−15 in both regions, showing no relationship to the different geotectonic settings. The uncontaminated brine and groundwater samples are likely to have retained the original 129I/127I ratios of marine I released from the old organic matter stored in sedimentary rock. 相似文献
99.
K. Ohta S. Takano S. Kagaya H. Yamada H. Minakami 《International journal of geographical information science》2013,27(6):687-698
To improve the geographical accessibility of neurosurgical emergency hospitals for elderly people, we developed several alternative site plans for a new neurosurgical emergency hospital in Sapporo, Japan. Hospitals, population data, routes, and the numerical information for the Analytic Hierarchy Process computations were input into a Geographical Information System. Pairwise comparison revealed the following weights which were assigned to each of the four criteria: 0.674 for availability of hospital beds; 0.169 for the maximum road distance of the shortest routes; 0.101 for the elderly population within a 3‐km radius; and 0.056 for the median road distance of the shortest routes. The alternative proposed could cover 4000 more elderly people in the 3‐km radius of the hospitals. The integration of Geographical Information Systems and the Analytic Hierarchy Process constitutes a powerful tool for analysing traffic conditions in mid‐sized cities and for suggesting city planning to improve prognosis of stroke. 相似文献
100.