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21.
Abstract– The Dawn spacecraft carries a gamma‐ray and neutron detector (GRaND), which will measure and map the abundances of selected elements on the surface of asteroid 4 Vesta. We compare the variability of moderately volatile/refractory incompatible element ratios (K/Th and K/Ti) in howardite, eucrite, and diogenite (HED) meteorites with those in other achondrite suites that represent asteroidal crusts, because these ratios may be accurately measured by GRaND and likely reflect initial chemical compositions of the HED parent body. The K/Th and K/Ti variations can differentiate HED meteorites from angrites and some unique eucrite‐like lithologies. The results suggest that K, Th, and Ti abundances determined from GRaND data could not only confirm that Vesta is the parent body of HED meteorites but might also allow recognition of as‐yet unsampled compositional terranes on Vesta. Besides the K‐Th‐Ti systematics study, we propose a new three‐component mixing model for interpretation of GRaND spectra, required because the spatial resolution of GRaND is coarser than the spectral (compositional) heterogeneity of Vesta’s surface. The mixing model uses abundances of K, Ti, Fe, and Mg that will be analyzed more accurately than other prospective GRaND‐analyzed elements. We examine propagated errors due to GRaND analytical uncertainties and intrinsic errors that stem from an assumption introduced into the mixing model. The error investigation suggests that the mixing model can adequately estimate not only the diogenite/eucrite mixing ratio but also the abundances of most major and minor elements within the GRaND propagated errors.  相似文献   
22.
Tomohiro  Toki  Toshitaka  Gamo  Urumu  Tsunogai 《Island Arc》2006,15(3):285-291
Abstract   We collected free-gas and in situ fluid samples up to a depth of 200.6 m from the Sagara oil field, central Japan (34°44'N, 138°15'E), during the Sagara Drilling Program (SDP) and measured the concentrations and stable carbon isotopic compositions of CH4 and C2H6 in the samples. A combination of the CH4/C2H6 ratios with the carbon isotope ratios of methane indicates that the hydrocarbon gases are predominantly of thermogenic origin at all depths. The isotope signature of hydrocarbon gases of δ13      < δ13     suggests that these gases in the Sagara oil field are not generated by polymerization, but by the decomposition of organic materials.  相似文献   
23.
Wave set-up in storm surges is studied using a numerical model for coasts in Tosa Bay, Japan, open to the Pacific Ocean. Simulation models employing only atmospheric pressures and winds as external forces are unable to properly simulate open coast storm surge heights, such as those due to Typhoon Anita (1970). However, the present study shows that a numerical model incorporating wave-induced radiation stresses, as well as wind stresses and pressure gradients, is able to account for the open coast surge heights. There is a maximum contribution of 40% by the radiation stresses to the peak sea level rises. This study also evaluates the effects of the tides; including the tides improves the agreement between the predicted water surface elevations and the observations. The difference in predictions between one-way coupling from wave to surge models and two-way coupling of the surge and wave models is found to be small.  相似文献   
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GPS精密测量在火山监测等地壳变动、山体滑坡监测中起到了非常有效的作用,已被广泛使用。但是,以前多在土木测量中使用的器材在实际监测中有很多限制,包括传感器、电源、通信等,如不做成系统很难体现出利用价值。笔者成功地将在恶劣气候条件下也能实施监测的系统实用化,并利用连续监测,通过统计处理达到高精度的实时变位监测。目前,日本有超过380个此类系统在通信、电源、环境条件均非常恶劣的现场运行着。我们应用此系统对四川雅安多营滑坡进行连续位移监测,并通过因特网实现位移监测数据的实时传输。经过近一年的监测证明,此系统监测精度高、运行稳定可靠[1~4]。  相似文献   
26.
Interaction between the external wall cladding and the seismic load resisting frame was examined in a full‐scale cyclic loading test of a three‐storey steel building structure. The building specimen had Autoclaved Lightweight Concrete (ALC, also designated as Autoclaved Aerated Concrete) panels installed and anchored to the structural frame as external wall cladding, using a standard Japanese method developed following the 1995 Kobe earthquake. ALC panelling is among the most widely used material for claddings in Japan. In the test, the ALC panel cladding contributed little to the stiffness and strength of the overall structure, even under a very large storey drift of 0.04 rad. No visible damage was noted in the ALC panels other than minor cracks and spalling of the bottom of the panels in the first storey. Consequently, in a Japanese steel building with properly installed ALC panel cladding, the structural frame is likely to be little affected by its cladding, and the ALC panels are capable of accommodating the maximum storey drift generally considered in structural design without sustaining discernible damage. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
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Laboratory experiments using a wave flume were designed to examine the threshold condition for ripple formation under asymmetrical oscillatory flows on an artificially roughened bed. Three types of sand beds were prepared in the experiments: they were flat, notched, and notch-mounded beds with bed roughness increasing in this order. The beds were constructed with three kinds of well-sorted sand with similar density, but different diameters. Data analyses were made using the two dimensionless parameters: the mobility number, M, a simplified form of the Shields number, and the Ursell number, U, a surrogate for asymmetry of flow field. The result confirmed that the threshold for ripple initiation is decreased with increasing bed perturbation and that as the bed perturbation increases, the dependency of this threshold on the flow asymmetry becomes less and finally null for the notch-mounded bed. This relationship is quantified by the following equations: M=17−14.5e−0.03U on the flat bed, M=5.0−2.5e−0.1U for the notched bed, and M=2.5 for the notch-mounded bed. A comparison between the previous field data and the present laboratory findings indicates that the threshold in the notch-mounded bed experiment, M=2.5, seems to provide a critical condition for rippling in the natural environment.  相似文献   
29.
Dawn has recently revealed that the surface of Vesta is heterogeneously covered by polymictic regoliths represented by mixtures of howardite, eucrite, and diogenite (HED) meteorites. Mixing relations of the HED suite are examined here using a new computational statistical approach of independent component analysis (ICA). We performed eight‐component ICA (Si, Ti, Al, Cr, Fe, Mn, Mg, and Ca) for 209 HED bulk‐rock compositions. The ICA results indicate that the HED bulk‐rock compositions can be reduced into three independent components (IC) and these IC vectors can reasonably explain compositional variation, petrographic observations, and the mixing relations of the HED suite. The IC‐1 vector represents a eucrite variation that extends from cumulate eucrite toward main‐group (MG) and incompatible‐element enriched eucrites. The IC‐2 vector represents a compositional variation of howardites that extends from diogenites to MG‐eucrites, indicating the well‐known two‐component mixing trend of diogenite and eucrite. The IC‐3 vector represents a compositional variation defined by diogenites and olivine‐bearing diogenites, suggesting mixing of olivine and orthopyroxene. Among the three ICs, the diogenite‐eucrite mixing trend IC‐2 is most statistically robust and dominates the compositional variations of the HED suite. Our ICA study further indicates that the combination of only three elements (Mg, Si, and Fe) approximates the eight‐component ICA model, and that the limited number of resolvable γ‐ray spectra obtained by the Dawn mission possibly discriminates olivine lithologies from the olivine‐free regolith breccias on the surface of Vesta.  相似文献   
30.
This paper introduces a new hydrographic climatology of the Okhotsk Sea; this climatology was constructed from the Far Eastern Regional Hydrometeorological Research Institute (FERHRI) database. The FERHRI database has a volume of data three to five times larger than the data used in previous studies because unpublished Russian observation data have been included in the FERHRI database. After removing erroneous data from the database by pertinent quality control methods, the climatology for 1/4°?×?1/4° grids is produced by applying objective analysis procedures. Features similar to those in previous studies are seen in the intermediate layers in the Okhotsk Sea, whereas our climatology provides values that fill in gaps in previous climatologies. It is obvious from the monthly climatologies that temperature and salinity distributions evolve in accordance with seasonal variations in the Eastern Sakhalin Current and inflow from the North Pacific. We also reconstructed climatologies for the winter mixed layer and dense shelf water from data obtained from the temperature minimum waters identified as the remnants of these two layers. Free access to the 1°?×?1° versions of all climatologies constructed in this study is available through the website.  相似文献   
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