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321.
日本结构控制的工程应用 总被引:4,自引:0,他引:4
提出了包括基础隔震系统、质量阻尼系统和其他阻尼器的结构振动控制系统,阐述了结构控制系统在日本的实际工程应用,同时还介绍了于2000年11月召开的第二届日本结构控制学术会议的情况. 相似文献
322.
Fractionation of azaarenes during oil migration 总被引:3,自引:0,他引:3
Masanobu Yamamoto 《Organic Geochemistry》1992,19(4-6)
A comparative study of alkylbenzoquinolines in crude oils and rock extracts (bitumens) from Japan and Sumatra shows that the ratios of nitrogen-masked isomers (NMIs) to nitrogen-exposed isomers (NEIs), and the ratio of higher homologs to lower homologs is higher in crude oils than in corresponding bitumens. Also, a regular increase in the ratios of NMIs to NEIs with increasing migration distance is observed for a series of crude oils from the Sarukawa Oil Field, northeastern Japan. These results are attributed to the preferential migration of NMIs caused by their weak adsorption on clay minerals and/or their low solubility in interstitial water, and the selective removal of lower honologs caused by their irreversible adsorption onto clays during oil migration, which are regarded as geochromatographic phenomena. It is suggested that those ratios can be used to estimate the degree of fractionation of oils during primary and secondary migration. 相似文献
323.
324.
Potential of submarine-cave sediments and oxygen isotope composition of cavernicolous micro-bivalve as a late Holocene paleoenvironmental record 总被引:2,自引:1,他引:1
Akihisa Kitamura Nagisa Yamamoto Tomoki Kase Shu-ichi Ohashi Mayumi Hiramoto Hitoshi Fukusawa Tsuyoshi Watanabe Tomohisa Irino Hiroshi Kojitani Michiyo Shimamura Ikuo Kawakami 《Global and Planetary Change》2007,55(4):301-316
A sediment layer (43 cm thick) and surface sediments (5 cm thick) in a submarine limestone cave (31 m water depth) on the fore-reef slope of Ie Island, off Okinawa mainland, Japan, were examined by visual, mineralogical and geochemical means. Oxygen isotope analysis was performed on the cavernicolous micro-bivalve Carditella iejimensis from both cored sediments and surface sediments, and the water temperature within the cave was recorded for nearly one year. These data show that: (1) water temperature within the cave is equal to that at 30 m deep in the open sea; (2) the biotic and non-biotic environments within the cave have persisted for the past 2000 years; (3) mud-size carbonate detritus is a major constituent of the submarine-cave deposit, and may have come mainly from the suspended carbonate mud produced on the emergent Holocene reef flat over the past two millennia; (4) the δ18O-derived temperature (Tδ18O) of C. iejimensis suggests that the species grows between April and July; (5) the Tδ18O of C. iejimensis from cored sediments implies that there were two warmer intervals, at AD 340 ± 40 and AD 1000 ± 40, which correspond to the Roman Warm Period and Medieval Warm Period, respectively. These suggest that submarine-cave sediments provide unique information for Holocene reef development. In addition, oxygen isotope records of cavernicolous C. iejimensis are a useful tool to reconstruct century-scale climatic variability for the Okinawa Islands during the Holocene. 相似文献
325.
Yoshiaki Ishihara Masaki Kanao Masa-yuki Yamamoto Shigeru Toda Takeshi Matsushima Takahiko Murayama 《地学前缘(英文版)》2015,6(2)
Characteristic infrasound waves observed at Antarctic stations demonstrate physical interaction involving environmental changes in the Antarctic continent and the surrounding oceans.A Chaparraltype infrasound sensor was installed at Syowa Station(SYO;39°E,69°S),East Antarctica,as one of the projects of the International Polar Year(IPY2007—2008).Data continuously recorded during the three seasons in 2008—2010 clearly indicate a contamination of the background oceanic signals(microbaroms)with peaks between 4 and 10 s observed during a whole season.The peak amplitudes of the microbaroms have relatively lower values during austral winters,caused by a larger amount of sea-ice extending around the L(u|")tzow-Holm Bay near SYO,with decreasing ocean wave loading effects.Microbaroms measurements are useful tool for characterizing ocean wave climate,complementing other oceanographic and geophysical data.A continuous monitoring by infrasound sensors in the Antarctic firmly contributes to the Comprehensive Nuclear-Test-Ban Treaty(CTBT) in the southern high latitude,together with the Pan-Antarctic Observations System(PAntOS) under the Scientific Committee on Antarctic Research(SCAR).Detailed measurements of the infrasound waves in Antarctica,consequently,could be a new proxy for monitoring regional environmental change as well as the temporal climate variations in the polar regions. 相似文献
326.
327.
A pronounced regional bathymetric swell is a common feature of oceanic hotspot volcanism. Recently, the hypothesis of a buoyant sublithospheric swell‐root has been favoured, the root being either a ‘refracted plume’ of hot, buoyant and hence low‐viscosity plume material embedded within surrounding higher viscosity asthenosphere, or a ‘restite‐root’ composed of hot and more viscous residues to hotspot melt‐extraction from the hottest central portion of the upwelling plume. In this article, we present numerical experiments that show that these two scenarios predict different flow and melting patterns whenever the plume passes beneath an obliquely oriented fracture zone where the base of the overriding lithosphere changes in thickness. We find that the restite‐root hypothesis predicts an asymmetric spatial pattern of persistent ‘arch volcanism’ strikingly similar to that found in the Hawaiian chain surrounding the Molokai Fracture Zone. In contrast, the ‘refracted plume’ hypothesis predicts more chaotic patterns quite different from the off‐chain pattern of Hawaiian volcanism. 相似文献
328.
Mutsuo Inoue Yusuke Nakano Yoko Kiyomoto Hisaki Kofuji Yasunori Hamajima Masayoshi Yamamoto 《Journal of Oceanography》2010,66(3):425-428
A total of 21 surface water samples were collected on the east side of the East China Sea (ECS) (3 sites) and at the Tsushima
Strait (1 site), and 226Ra and 228Ra activities were measured using low-background γ-spectrometry. The 228Ra/226Ra ratios among the samples exhibited notable seasonal variation (228Ra/226Ra = 0.2–2.6) accompanying changes of salinity (31.7–34.7). Seasonal water circulation within the ECS is hypothesized to cause
the change by altering the mixing ratio of 228Ra-rich continental shelf water and 228Ra-poor Kuroshio water. 相似文献
329.
Hajime Kawakami Makio C. Honda Kazuhiko Matsumoto Tetsuichi Fujiki Shuichi Watanabe 《Journal of Oceanography》2010,66(1):71-83
Observations of primary productivity, 234Th, and particulate organic carbon (POC) were made from west to east across the northern North Pacific Ocean (from station
K2 to Ocean Station Papa) during September–October 2005. Primary productivities in this region varied longitudinally from
approximately 236 to 444 mgC m−2d−1 and clearly indicate the West High East Low (WHEL) trend. We estimated east-west variations in the POC flux from the surface
layer (0–100 m) by using 234Th as a tracer. POC fluxes in the western region (44–53 mgC m−2d−1) were higher than those in the eastern region (21–34 mgC m−2d−1). However, the export ratios (e-ratios) ranged from approximately 8% to 16% and did not show the WHEL trend. Contrary to our expectation, no relation between
POC flux (or e-ratio) and diatom biomass (or dominance) was apparent in autumn in the northern North Pacific. 相似文献
330.
Biomass and primary productivity of benthic microalgae (BMA) and planktonic algae in Suo Nada, the western part of the Seto
Inland Sea, Japan were compared in terms of unit area with regard to their seasonal and spatial distribution in 2002. Judging
from light compensation depth and water depth, the southwestern part of Suo Nada was considered to be a potential habitat
for BMA. Whereas the contribution of sedimented planktonic algae was high in biomass at the sediment surface, BMA was obviously
significant both in biomass and primary production in the shallow southwestern part. However, the contribution of BMA to the
total biomass in the entire water column was 7% in winter and 2% in summer. The primary production of BMA varied between 4.0
and 74.0 mg C m−2 d−1 in the southwestern part, accounting for 2–12% of the whole water column primary production. The ecological roles of BMA
in the Suo Nada ecosystem are discussed, such as reduction of benthic nutrient flux, oxidation of surface sediments and feed
for higher animals. 相似文献