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31.
32.
Shigeaki Ono Tsuyoshi Iizuka Takumi Kikegawa 《Physics of the Earth and Planetary Interiors》2005,150(4):331-338
In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch–Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of ρ0 = 3.888 g/cm3 and a bulk modulus of K0 = 229 ± 9 GPa for K′0 = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at K′0 = 4, then the value of K0 = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase. 相似文献
33.
In order to reconstruct the architectural evolution of a fault zone with heterogeneous structures, we studied the Atera Fault in Central Japan, and described the detailed mesoscopic and microscopic features of the zone. The fault zone studied consists of a 1.2‐m wide fault core of fault breccia mixed with fragments derived from welded tuff, granite, and mafic volcanic rocks. The 1.2‐m wide fault core is bordered by a western damage zone characterized by a welded tuff fault breccia and an eastern damage zone characterized by a granite cataclasite. A secondary fault core, a 30‐cm wide granite‐derived fault gouge, cross‐cuts the granite cataclasite. Although welded tuff fault breccia and granite cataclasite are also pervasively fractured and fragmented, the fault cores are significantly affected by fragment size reduction due to intense abrasive wear and comminution. The 1.2‐m wide fault core includes fragments and a sharp dark layer composed of mafic volcanic rocks, which can be correlated with neighboring 1.6 Ma volcanic rocks. This observation places a younger constraint on the age of the fault core formation. Carbonate coating on basalt fragments in the 1.2‐m wide fault core has also been fractured indicating the repetition of intense fragmentation. Bifurcated, black and gray veins near the 1.2‐m wide fault core are likely injection veins, formed by the rapid injection of fine material within fault zones during seismic events. The granite‐derived fault gouge, characterized by hard granite fragments without intense brecciation and microfracturing, in a kaolinite‐rich clay matrix, is interpreted as the most recent slip zone within the exposed fault zone. A preview of published geological and hydrological studies of several fault zones shows that clay‐rich fault cores can exhibit much lower permeability than the adjacent damage zones represented in this present case by the welded tuff fault breccia and granite cataclasite. 相似文献
34.
Sayaka Yasunaka Yukihiro Nojiri Taketo Hashioka Chisato Yoshikawa Taketoshi Kodama Shin-ichiro Nakaoka Sanae Chiba Fuminori Hashihama Masahide Wakita Ken Furuya Daisuke Sasano Akihiko Murata Hiroshi Uchida Michio Aoyama 《Journal of Oceanography》2018,74(1):1-11
We used more than 25,000 nutrient samples to elucidate for the first time basin-scale distributions and seasonal changes of surface ammonium (NH4 +) and nitrite (NO2 ?) concentrations in the Pacific Ocean. The highest NH4 +, NO2 ?, and nitrate (NO3 ?) concentrations were observed north of 40°N, in the coastal upwelling region off the coast of Mexico, and in the Tasman Sea. NH4 + concentrations were elevated during May–October in the western subarctic North Pacific, May–December in the eastern subarctic North Pacific, and June–September in the subtropical South Pacific. NO2 ? concentrations were highest in winter in both hemispheres. The seasonal cycle of NH4 + was synchronous with NO2 ?, NO3 ?, and satellite chlorophyll a concentrations in the western subtropical South Pacific, whereas it was synchronous with chlorophyll-a but out of phase with NO2 ? and NO3 ? in the subarctic regions. 相似文献
35.
Hiroaki?KondoEmail author Yutaka?Genchi Yukihiro?Kikegawa Yukitaka?Ohashi Hiroshi?Yoshikado Hiroshi?Komiyama 《Boundary-Layer Meteorology》2005,116(3):395-421
A multilayer one-dimensional canopy model was developed to analyze the relationship between urban warming and the increase
in energy consumption in a big city. The canopy model, which consists of one-dimensional diffusion equations with a drag force,
has three major parameters: building width, distance between buildings, and vertical floor density distribution, which is
the distribution of a ratio of the number of the buildings that are taller than some level to all the buildings in the area
under consideration. In addition, a simplified radiative process in the canopy is introduced. Both the drag force of the buildings
and the radiative process depend on the floor density distribution. The thermal characteristics of an urban canopy including
the effects of anthropogenic heat are very complicated. Therefore, the focus of this research is mainly on the basic performance
of an urban canopy without anthropogenic heat. First, the basic thermal characteristics of the urban canopy alone were investigated.
The canopy model was then connected with a three-dimensional mesoscale meteorological model, and on-line calculations were
performed for 10 and 11 August, 2002 in Tokyo, Japan. The temperature near the ground surface at the bottom of the canopy
was considerably improved by the calculation with the canopy model. However, a small difference remained between the calculation
and the observation for minimum temperature. Deceleration of the wind was well reproduced for the velocity at the top of the
building by the calculation with the canopy model, in which the floor density distribution was considered. 相似文献
36.
Ayako?ShinozakiEmail author Hisako?Hirai Hiroyuki?Kagi Tadashi?Kondo Taku?Okada Daisuke?Nishio-Hamane Shin-ichi?Machida Tetsuo?Irifune Takumi?Kikegawa Takehiko?Yagi 《Physics and Chemistry of Minerals》2012,39(2):123-129
High pressure and temperature reactions of a mixture of forsterite and hydrogen molecules have been carried out using a laser
heated diamond anvil cell at 9.8–13.2 GPa and ~1,000 K. In situ X-ray diffraction measurements showed no sign of decomposition
or phase transitions of the forsterite under these experimental conditions, indicating that the olivine structure was maintained
throughout all runs. However, a substantial expansion of the unit cell volume of the forsterite was observed for samples down
to ~3 GPa upon quenching to ambient pressure at room temperature. The Raman spectroscopy measurements under pressure showed
significant shifts of the Raman peaks of the Si–O vibration modes for forsterite and of the intramolecular vibration mode
for H2 molecules toward a lower frequency after heating. Additionally, no OH vibration modes were observed by Raman and FT-IR spectroscopic
measurements. These lines of evidence show that the observed volume expansion in forsterite is not explained by the incorporation
of hydrogen atoms as hydroxyl, but suggest the presence of hydrogen as molecules in the forsterite structure under these high
pressure and temperature conditions. 相似文献
37.
Peng K. Hong Hiroko Miyahara Yusuke Yokoyama Yukihiro Takahashi Mitsuteru Sato 《Journal of Atmospheric and Solar》2011,73(5-6):587-591
We examined the effect of the 11-year solar cycle and quasi-biennial oscillation (QBO) on the ~27-day solar rotational period detected in tropical convective cloud activity. We analyzed the data of outgoing longwave radiation (OLR) for AD1979–2004, dividing into four different cases by the combination of high and low solar activities in terms of the 11-year variation, and easterly and westerly stratospheric winds associated with QBO. As a result, ~27-day variation has been most significantly detected in high solar activity period around the Indo-Pacific Warm Pool. Based on correlation analysis, we find that solar rotation signal can explain 10–20% of OLR variability around the tropical warm pool region during the high solar activity period. The spatial distribution has been, however, apparently different according to the phases of QBO. It is suggested that the 11-year solar cycle and stratospheric QBO have a possibility to cause large-scale oceanic dipole phenomena. 相似文献
38.
Yukihiro Kikegawa Ai Tanaka Yukitaka Ohashi Tomohiko Ihara Yoshinori Shigeta 《Theoretical and Applied Climatology》2014,117(1-2):175-193
In this study, the sensitivities of surface air temperatures to anthropogenic heat (AH) were investigated in downtowns of the two Japanese major cities, Tokyo and Osaka. First, meteorological measurements were made with the simultaneous monitoring of electricity demand in a contrastive couple of a downtown commercial area (C-area) and a residential area (R-area) within each city in summer 2007. From the measurements, the areal-mean surface air temperatures were obtained as \( {\overline{T}}_{\mathrm{C}} \) and \( {\overline{T}}_{\mathrm{R}} \) for each of the C-area and R-area, respectively. Using the actual electricity demand and the estimated motor fuels consumption, their areal total was evaluated as the energy-consumption-basis AH. The estimated C-areas' AH indicated greater values up to 220 W/m2 on weekdays and remarkable decrease about by half on weekends, whereas that in the R-areas showed less values of 10–20 W/m2 stably. Then, \( {\overline{T}}_{\mathrm{C}}-{\overline{T}}_{\mathrm{R}} \) on calm and fine days were found to be systematically decreased from weekdays to weekends in both cities roughly indicating a proportional relationship with the reductions in the C-areas' AH on weekends. The result suggested a common afternoon sensitivity for both C-areas of around 1.0°C/100 W/m2, which indicated an intensity of the AH impact on surface air temperature there. Next, to simulate the observed AH impact, the authors' CM-BEM (a multilayer urban canopy model coupled with a building energy model) was newly implemented in the mesoscale Weather Research and Forecasting (WMF) model. This new system, WRF-CM-BEM, was applied to Tokyo and almost reasonably validated from the aspects of the reproducibility of urban surface air temperature and electricity demand in the observation areas. The simulations also suggested that WRF-CM-BEM underestimated the observed air temperature sensitivity to AH in the Tokyo C-area roughly by half but still in the same order of magnitude. 相似文献
39.
Mitsuo Uematsu Katsumoto Kinoshita Yukihiro Nojiri 《Journal of Atmospheric Chemistry》2000,35(2):151-163
Direct deposition measurements ofatmospheric insoluble particles over the sub-ArcticNorth Pacific indicate that the number of particles(6.4 ± 3.8) × 104 cm-2 per rain eventwas fairly constant compared with the large variationof the precipitation rate, which ranged from 0.16 to18 mm per event for 43 rain days during the period ofMarch–September (total 109 days) 1996. Thissuggests that insoluble particles larger than 0.4 min area equivalent diameter are primarilyremoved at the margin of the rainfall area by wetscavenging processes below clouds in the marineatmosphere in sub-Arctic regions. The frequency ofrain events controls the fate of the troposphericaerosols larger than sub-micrometer in diameter. Reflecting the seasonal long-range transport of Asiandust, mineral particles were dominant as insolubleparticles in the spring rains, but carbonaceousparticles were dominant in the summer rains. Theatmospheric deposition of insoluble particles could besignificant as a source of sediment particles over thesub-Arctic North Pacific. 相似文献
40.
High-pressure and high-temperature experiments using a laser-heated diamond anvil cell (LHDAC) and synchrotron X-ray diffraction have revealed a phase transition in MgAl2O4. CaTi2O4-type MgAl2O4 was found to be stable at pressures between 45 and at least 117 GPa. The transition pressure of CaTi2O4-type phase in MgAl2O4 is much lower than that in the natural N-type mid-oceanic ridge basalt composition. The Birch–Murnaghan equation of state for CaTi2O4-type MgAl2O4 was determined from the experimental unit cell parameters with K
0=219(±6) GPa, K
0′=4(constrained value), and V
0=238.9(±9) Å3. The observed compressibility was in agreement with the theoretical compressibility calculated in a previous study. ε-MgAl2O4 was observed at pressures between 40 and 45 GPa, which has not been reported in natural rock compositions. The gradient (dP/dT slope) of the transition from the ε-type to CaTi2O4-type MgAl2O4 had a positive value. These results should resolve the dispute regarding the stable high-pressure phase of MgAl2O4, which has been reported in earlier studies using both the multi-anvil press and the diamond anvil cell. 相似文献