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41.
Yuzo Ohnishi Tomofumi Koyama Ikuo Hagiwara Shigeru Miki Testuya Shimauchi 《Geomechanics and Geoengineering》2014,9(2):97-112
This paper discussed the analytical precision on equations of motion in some practical studies that use 2-D DDA, 2D-Coupled analysis of NMM & DDA, and 3D-DDA. We point out the main reason for numerical instability in DDA is loss of the effective digits when superposing the global stiffness matrix under the variable conditions of large and the small blocks. Categories of analyses are distributed in 2D-DDA static masonry structures such as the Great Pyramid and the Pont du Gard, 2D-DDA dynamic rock fall problems and the sensitivity of its analysis on the velocity ratio and the penalty, earthquake response analysis of rock slopes, 2D-NMM, 2D-coupled analysis of DDA and NMM and 3D-DDA rock fall problem. The selected examples on the Great Pyramid, Pont du Gard and Bayon Temple at Angkor Thom are located in Egypt, France and Cambodia respectively as UNESCO world heritages sites. The authors evaluated the applicability of the methods and the reliability of the results by comparing different methods and site observations from the practical problems. 相似文献
42.
Tetsuo Kawakami Shigeru Sueoka Tatsunori Yokoyama Saya Kagami Georgina E. King Frédéric Herman Sumiko Tsukamoto Takahiro Tagami 《Island Arc》2021,30(1):e12414
Solidification pressure and crystallization age of the ~5 Ma Shiaidani Granodiorite (Hida Mountain Range, central Japan) are determined based on Al-in-hornblende geobarometry and U–Pb zircon dating. Al-poor patchy replacements developed in amphiboles are common in this granite and petrographic study revealed that the replacements include chloritized biotite and albitic plagioclase. These are probably the hydrothermally recrystallized domains, and should not be used for solidification pressure estimates. Magmatic rim of amphibole is characterized by Si < 7.3 a.p.f.u. (AlIV > 0.7 a.p.f.u.), and utilized in solidification pressure estimate that yielded 0.17–0.29 GPa. The solidification age of the granite is estimated as ~5.6–5.2 Ma using U–Pb zircon dating. From these data, the lower limit of an average denudation rate after ~5.6–5.2 Ma for the area where Shiaidani Granodiorite is exposed is estimated as 0.93–2.5 mm/year. 相似文献
43.
Tatsuya Fujimoto Shigeru Otoh Yuji Orihashi Takafumi Hirata Takaomi D. Yokoyama Masanori Shimojo Yoshikazu Kouchi Hokuto Obara Yasuo Ishizaki Kazuhiro Tsukada Toshiyuki Kurihara Manchuk Nuramkhan Sersmaa Gonchigdorj 《Resource Geology》2012,62(4):408-422
A dropstone‐bearing, Middle Permian to Early Triassic peri‐glacial sedimentary unit was first discovered from the Khangai–Khentei Belt in Mongolia, Central Asian Orogenic Belt. The unit, Urmegtei Formation, is assumed to cover the early Carboniferous Khangai–Khentei accretionary complex, and is an upward‐fining sequence, consisting of conglomerates, sandstones, and varved sandstone and mudstone beds with granite dropstones in ascending order. The formation was cut by a felsic dike, and was deformed and metamorphosed together with the felsic dike. An undeformed porphyritic granite batholith finally cut all the deformed and metamorphosed rocks. LA‐ICP‐MS, U–Pb zircon dating has revealed the following 206Pb/238U weighted mean igneous ages: (i) a granite dropstone in the Urmegtei Formation is 273 ± 5 Ma (Kungurian of Early Permian); (ii) the deformed felsic dike is 247 ± 4 Ma (Olenekian of Early Triassic); and (iii) the undeformed granite batholith is 218 ± 9 Ma (Carnian of Late Triassic). From these data, the age of sedimentation of the Urmegtei Formation is constrained between the Kungurian and the Olenekian (273–247 Ma), and the age of deformation and metamorphism is constrained between the Olenekian and the Carnian (247–218 Ma). In Permian and Triassic times, the global climate was in a warming trend from the Serpukhovian (early Late Carboniferous) to the Kungurian long and severe cool mode (328–271 Ma) to the Roadian to Bajocian (Middle Jurassic) warm mode (271–168 Ma), with an interruption with the Capitanian Kamura cooling event (266–260 Ma). The dropstone‐bearing strata of the Urmegtei Formation, together with the glacier‐related deposits in the Verkhoyansk, Kolyma, and Omolon areas of northeastern Siberia (said to be of Middle to Late Permian age), must be products of the Capitanian cooling event. Although further study is needed, the dropstone‐bearing strata we found can be explained in two ways: (i) the Urmegtei Formation is an autochthonous formation indicating a short‐term expansion of land glacier to the central part of Siberia in Capitanian age; or (ii) the Urmegtei Formation was deposited in or around a limited ice‐covered continent in northeast Siberia in the Capitanian and was displaced to the present position by the Carnian. 相似文献
44.
Kaori Jogo Motoo Ito Shigeru Wakita Sachio Kobayashi Jong Ik Lee 《Meteoritics & planetary science》2019,54(5):1133-1152
We observed metamorphosed clasts in the CV3 chondrite breccias Graves Nunataks 06101, Vigarano, Roberts Massif 04143, and Yamato‐86009. These clasts are coarse‐grained polymineralic rocks composed of Ca‐bearing ferroan olivine (Fa24–40, up to 0.6 wt% CaO), diopside (Fs7–12Wo44–50), plagioclase (An52–75), Cr‐spinel (Cr/[Cr + Al] = 0.4, Fe/[Fe + Mg] = 0.7), sulfide and rare grains of Fe‐Ni metal, phosphate, and Ca‐poor pyroxene (Fs24Wo4). Most clasts have triple junctions between silicate grains. The rare earth element (REE) abundances are high in diopside (REE ~3.80–13.83 × CI) and plagioclase (Eu ~12.31–14.67 × CI) but are low in olivine (REE ~0.01–1.44 × CI) and spinel (REE ~0.25–0.49 × CI). These REE abundances are different from those of metamorphosed chondrites, primitive achondrites, and achondrites, suggesting that the clasts are not fragments of these meteorites. Similar mineralogical characteristics of the clasts with those in the Mokoia and Yamato‐86009 breccias (Jogo et al. 2012 ) suggest that the clasts observed in this study would also form inside the CV3 chondrite parent body. Thermal modeling suggests that in order to reach the metamorphosed temperatures of the clasts of >800 °C, the clast parent body should have accreted by ~2.5–2.6 Ma after CAIs formation. The consistency of the accretion age of the clast parent body and the CV3 chondrule formation age suggests that the clasts and CV3 chondrites could be originated from the same parent body with a peak temperature of 800–1100 °C. If the body has a peak temperature of >1100 °C, the accretion age of the body becomes older than the CV3 chondrule formation age and multiple CV3 parent bodies are likely. 相似文献
45.
The effect of a tidal cycle on the dynamics of nutrients in a tidal estuary in the Seto Inland Sea, Japan 总被引:4,自引:0,他引:4
Shigeru Montani Paolo Magni Megumi Shimamoto Nao Abe Koichi Okutani 《Journal of Oceanography》1998,54(1):65-76
A 24 hour time series survey was carried out during a spring tide (tidal range ca.2 m) of May 1995 on a tidal estuary in the
Seto Inland Sea, Japan, in the context of an integrated program planned to quantify the dynamics of biophilic elements (carbon,
nitrogen and phosphorus) and the roles played by the macrobenthos on the processes. Three stations were set along a transect
line of about 1.4 km, which linked the river to the rear to the innermost part of the subtidal zone. Every hour, at each station,
measurements were made of surface water temperature, salinity and dissolved oxygen concentration, and surface water was collected
for the determination of nutrients [NH4
+−N, (NO3
−+NO2
−)−N, PO4
3−−P and Si (OH)4−Si]. During the ebb flow, riverine input of silicate and nitrate+nitrite significantly increased the concentrations of both
the intertidal and the subtidal stations. Conversely, during the high tide, river nutrient concentrations were lowered by
the mixing of fresh water with sea water. As a result, best (inverse) correlations were found at the river station for salinity
against silicate (y=-2.9 Sal.+110.7,r
2=0.879) and nitrate+nitrite (y=-1.3 Sal.+48.4,r
2=0.796). In contrast, ammonium nitrogen concentrations were higher at intermediate salinities. Indeed, no significant correlation
was found between salinity and ammonium. The effect of the macrobenthos, which is abundant on the intertidal flat, is discussed
as a biological component that influences the processes of nutrient regeneration within the estuary. The effect of the tidal
amplitude is an important one in determining the extent of the variations in nutrient concentrations at all three stations,
which were stronger between the lower low tide and the higher high tide. 相似文献
46.
Over the Southern Ocean the dominant modes of the atmospheric field are known as the Southern Annular Mode (SAM) or Antarctic
Oscillation, and the Pacific South American (PSA) pattern. Statistical analysis of sea surface wind (SSW) from satellite observation
revealed two leading modes of SAM-like and PSA patterns. In the high latitudes, the SAM-like pattern of the SSW had a large
amplitude over the Bellingshausen Basin and Australian-Antarctic Basin, with opposite phase between the two basins. On the
intraseasonal time scale, large-scale sea surface height (SSH) also had notable variability, showing a basin-scale anti-phase
mode over the two basins. To explain the response of oceanic variations to these atmospheric modes, we analyzed the relationship
between the dominant modes of wind stress and large-scale SSH on the intraseasonal time scale. The SAM-like pattern of wind
stress was correlated with the SSH variation over the two basins. The SSH basin mode was most simply explained by a simple
barotropic response to the SAM-like mode of wind stress, with the curl of opposite phase between the two basins. We conclude
that the zonal asymmetry of the wind field of the SAM plays an important role in driving the antiphase SSH basin modes. 相似文献
47.
We have developed a semi-analytic method of calculating the changes in heliocentric Keplerian orbital elements due to gravitational scattering by a protoplanet as a three-body problem. In encounters with high incident velocities, either the gravity of the protoplanet or the solar gravity can be regarded as perturbation force. In close encounters, by taking into account the solar gravity as a perturbation, we modified the two-body gravitational scattering. On the other hand, in slightly distant encounters, we apply the perturbing force of the protoplanet to the heliocentric Keplerian orbit of planetesimals. As a result, as for high-velocity encounters, the three-body problem is semi-analytically solvable. Our semi-analytic method can reproduce the numerical result of the orbital changes of individual planetesimals for the broad range of high-energy encounters with surprising high accuracy. We found that our method is valid under the conditions (i)b0? 2 and (ii) (e20+i20− b20)1/2? 4, wheree0andi0are eccentricity and inclination of relative motion normalized by the reduced Hill radius andb0is the difference between semimajor axes normalized by the Hill radius. Though our method needs some numerical procedure, its cpu time is negligibly short compared with that of the direct orbital integration. In simulation of orbital evolution of planetesimals around a protoplanet in the gas, which we will perform in the subsequent paper, most encounters can be calculated by the semi-analytic method. This makes it possible to perform the long term (∼105years) orbital calculation of ∼103–4planetesimals. 相似文献
48.
Shigeho Sueno Shigeru Matsuura G. V. Gibbs M. B. Boisen Jr. 《Physics and Chemistry of Minerals》1998,25(5):366-377
Two new protoamphibole-type amphiboles with space group type Pnmn, have been found in nature: protoferro-anthophyllite (Fe0.80Mn0.20)2 (Fe0.98Mg0.02)5 (Si4O11)2(OH)2, and protomangano-ferro-anthophyllite, (Mn0.70Fe0.30)2 (Fe0.82Mg0.18)5 (Si4O11)2(OH)2. Protoferro-anthophyllite (PFA) occurs in pegmatites at both Gifu Prefecture, Japan and at Cheyenne Mountain, El Paso County, Colorado, USA. Protomangano-ferro-anthophyllite, (PMFA) occurs in pegmatites at Fukushima Prefecture and in a Mn mine at Tochigi Prefecture, Japan. Structure determinations of the two amphiboles show that both are isostructural with the synthetic fluorian-amphibole, protoamphibole (= protofluorian-lithian-anthophyllite). A calculation of the procrystal electron density distributions, the bond paths and the bond critical point properties of PFA, PMFA, grunerite and protoamphibole indicates that the M4 cation in these amphiboles is 4-coordinated. A calculation of the electron density distributions at the Becke3LYP/6-311G(2d,p) level for model silicate tetrahedra for these amphiboles and anthophyllite reveals that the value of the electron density at the bond critical points, ρ(r c ), for the SiO(nbr) bonds is larger, on average (0.93 e/Å3), than that for the SiO(br) bonds (0.90 e/Å3). The observed SiO bond lengths decrease linearly with increasing ρ(r c ) while the magnitudes of the curvatures of ρ(r c ) both perpendicular and parallel to the bonds and the Laplacian of ρ(r c ) each increases. These trends are associated with an increase in the electronegativity of the Si cation, a possible increase in the covalent character of the SiO bond and a tendency for SiO(nbr) bonds to be involved in wider OSiO angles than SiO(br) bonds. It is possible, if not likely, that protoanthophyllite has often been misidentified as anthophyllite. 相似文献
49.
A method is described to estimate the chemical forms of arsenic (As) and antimony (Sb) in a variety of geochemical reference materials, combining a sequential extraction scheme with hydride generation and atomic absorption spectrometry (HG-AAS). The fractions dissolved by sequential extraction are empirically defined as the exchangeable, EDTA soluble, oxide, sulfide and residual fractions. The amount of As and Sb in the EDTA soluble fraction have been derived mainly from oxide phases, and partly from carbonate minerals. Most sulfide minerals in common geological samples were considered to be dissolved with the digestion of 0.7 mol l−1 NaOCl, but only small fraction of arsenopyrite and loellingite in ores could be dissolved in this way. Satisfactory agreement was observed between the sum of the As or Sb values from exchangeable to residual fractions and the reported total As or Sb values, with a few exceptions. Analytical results of As and Sb for thirty five geochemical reference materials are tabulated, and geochemical and mineralogical features are discussed. 相似文献
50.
Takuya Echigo Tamao Hatta Seiko Nemoto Shigeru Takizawa 《Physics and Chemistry of Minerals》2012,39(9):769-778
We examined the effects of crystallinity and crystal morphology on surface hydroxyl concentration of goethite using four kinds of goethite samples prepared by aging a hydrous ferric oxide (ferrihydrite) at different temperatures ranging from 4 to 70?°C. These samples were analyzed with the following methods: powder X-ray diffraction, Brunauer–Emmett–Teller surface area analyzer, atomic force microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and high-resolution X-ray photoelectron spectroscopy (XPS). The first three analyses showed that the goethite aged at lower temperature has lower crystallinity, smaller particle size and lower aspect ratio. The ATR-FTIR analysis revealed that the OH-stretching band of goethite aged at 4?°C moves to slightly higher wavenumber than those of the samples aged at higher temperatures. Their XPS analyses demonstrated that variation in the concentration of surface hydroxyl group ranges from 6.6 (nm?2) for the sample aged at 4?°C to 7.7 (nm?2) for the sample aged at 70?°C. Considering the analytical depth of the XPS (~5?nm), photoelectrons are emitted from the uppermost layers of the analyte. Hence, XPS results are interpreted to reflect variations in the morphology of fine crystals (<100?nm thick). The morphology of the present goethites can be characterized by their aspect ratio, in other words, the degree of development of (110)–(110) intersection edges at which protons preferentially accumulate. This variation in the concentration of surface hydroxyl group revealed by XPS analysis offers experimental evidence for the effects of crystallinity and morphology on the surface chemical properties of goethite. 相似文献