Effect of oxygen partial pressure on the dislocation recovery in olivine: a new constraint on creep mechanisms     

Shun-ichiro Karato  Hiroki Sato 《Physics of the Earth and Planetary Interiors》1982,28(4):312-319

The dislocation annihilation rate in experimentally deformed olivine single crystals was measured as a function of oxygen partial pressure (P_O2). It was shown that the dislocation annihilation rate decreased with increasing P_O2. This result is inconsistent with the reported P_O2 dependence of creep rate () in single olivine crystals, thus indicating that the creep in single olivine crystals is not rate-controlled by recovery, under the experimentally investigated conditions.  相似文献   

A three‐component end‐member analysis of streamwater hydrochemistry in a small Japanese forested headwater catchment     

Masanori Katsuyama  Nobuhito Ohte  Sumiji Kobashi 《水文研究》2001,15(2):249-260

Intensive water sampling in conjunction with hydrological observations was conducted during three different rainstorms in order to understand the effects of rainfall events on the temporal variation of streamwater chemistry in a small headwater forest catchment. Concentrations of Na⁺ and SO₄^2? decreased as the discharge rate increased. Hydrograph separation of the components was made using the three‐component model based on the end‐members mixing analysis (EMMA). The three end‐members were:

• 1 the groundwater in the saturated zone that prescribes the chemistry of the baseflow;
• 2 the throughfall that dilutes the streamwater;
• 3 the groundwater in the transient saturated zone prescribed, which was dependent on the groundwater level.

When the groundwater level was lower, only the two components, groundwater in the saturated zone and throughfall, affected the streamwater chemistry. When the groundwater level rose and the saturated zone spread, the groundwater in the transient saturated zone became the third component. When the groundwater in the transient saturated zone contributed to the discharge, this component became the dominant source and the streamwater chemistry was affected by the groundwater chemistry in the transient saturated zone. When this component was discharged as the saturation overland flow, the streamwater chemistry was greatly affected by this component. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Rockfall hazard in the Daisekkei Valley, the northern Japanese Alps, on 11 August 2005     

Yoshihiko Kariya  Go Sato  Kuniyasu Mokudai  Jiro Komori  Masaki Ishii  Ryoko Nishii  Yosuke Miyazawa  Noriko Tsumura 《Landslides》2007,4(1):91-94

This paper describes a rockfall event in the Daisekkei Valley of Mount Shirouma-dake (2,932 m), the northern Japanese Alps. The rockfall occurred on a steep cliff comprising well-jointed felsites and produced debris of ≥8,000 m³. Most debris was deposited on an elongated snowpatch located immediately beneath the cliff, and it caused casualties among people who were trekking along a trail on the snowpatch. Additionally, a large rock block slipped 1 km on the snowpatch. The rockfall could have been due to the differential retreat of the rockwall, which contains areas of high- and low-density joints. Seasonal and diurnal freeze–thaw activities and snow avalanches and wash appear to be important factors responsible for the retreat. Although some rock blocks that can collapse further remain on the rockwall, the position of the mountain trail in the Daisekkei Valley is fixed. Fundamental reform of tourism systems for climbers, including education on natural hazards, is required.  相似文献   

Carbonate deposits on submerged seamounts in the northwestern Pacific Ocean     

Hideko  Takayanagi  Yasufumi  Iryu  Tsutomu  Yamada  Motoyoshi  Oda  Kazuyuki  Yamamoto  Tokiyuki  Sato  Shun  Chiyonobu  Akira  Nishimura  Tsutomu  Nakazawa  Satoshi  Shiokawa 《Island Arc》2007,16(3):394-419

Abstract   The lithology of shallow-water carbonates collected from 19 sites on 16 seamounts in six areas of the northwestern Pacific Ocean using the Deep-sea Boring Machine System are described. The areas include the Amami Plateau, Daito Ridge, Oki-Daito Ridge, Urdaneta Plateau, Kyushu-Palau Ridge and Ogasawara Plateau. Chronological constraint is provided by calcareous nannofossil biostratigraphy, planktonic foraminiferal biostratigraphy, larger foraminiferal biostratigraphy and strontium (Sr) isotope stratigraphy. Large amounts of shallow-water carbonates accumulated on the seamounts during the Oligocene, a relatively cool period, whereas limited carbonate deposits formed during the Early Miocene, a relatively warm period. This might indicate that deposition of shallow-water carbonates on seamounts in the northwestern Pacific Ocean was not necessarily controlled by climatic conditions, but was related to volcanism and tectonics that served as foundations for reef/carbonate-platform formation. Remarkable differences in biotic composition exist between Cretaceous and Cenozoic shallow-water carbonates. Late Cretaceous shallow-water carbonates are distinguished by the occurrence of rudists, solenoporacean algae and microencrusters. Middle Eocene to Early Oligocene shallow-water carbonates are dominated by Halimeda or nummulitid and discocyclinid larger foraminifers. Scleractinian corals became common from the Oligocene onward. Nongeniculate coralline algae and larger foraminifers were common to abundant throughout the Eocene to the Pleistocene. The replacement of major carbonate producers in the shallow-water carbonate factory during post-Cretaceous time is in accordance with previous studies and is considered to reflect a shift in seawater chemistry.  相似文献   

Non‐linear system identification of the versatile‐typed structures by a novel signal processing technique     

Jian Zhang  Tadanobu Sato  Susumu Iai 《地震工程与结构动力学》2007,36(7):909-925

Non‐linear structural identification problems have raised considerable research efforts since decades, in which the Bouc–Wen model is generally utilized to simulate non‐linear structural constitutive characteristic. Support vector regression (SVR), a promising data processing method, is studied for versatile‐typed structural identification. First, a model selection strategy is utilized to determine the unknown power parameter of the Bouc–Wen model. Meanwhile, optimum SVR parameters are selected automatically, instead of tuning manually. Consequently, the non‐linear structural equation is rewritten in linear form, and is solved by the SVR technique. A five‐floor versatile‐type structure is studied to show the effectiveness of the proposed method, in which both power parameter known and unknown cases are investigated. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

A New Coastal Marine Ecosystem Model Study Coupled with Hydrodynamics and Tidal Flat Ecosystem Effect   总被引：3，自引：0，他引：3  

Akio Sohma  Yasuyuki Sekiguchi  Hiroshi Yamada  Tatsuaki Sato  Kisaburo Nakata 《Marine pollution bulletin》2001,43(7-12):187-208

A new coastal marine ecosystem model was developed, which was composed of pelagic and benthic ecosystems, and was applied to Mikawa Bay, Japan. This model deals with variations of biochemical and physical interactions among dissolved oxygen and C–N–P species (composition formed out of carbon, nitrogen and phosphorus elements) so that it resolves the flux dynamics of carbon, nitrogen, phosphorus and oxygen elements. The physical and biochemical mechanism figured in this model is constructed for the purpose of simulating the estuarine lower trophic ecosystem, in areas where the sea was too deep for light to reach the sea-bottom. As a result of coupling the benthic with pelagic system, the effect of process of sedimentation and nutrient diffusion back to the pelagic system could be indicated. In addition, by implementing the tidal flat ecosystem model's calculation result, the integrated model can include the effect of water purification in tidal flats where the light can reach the sea-bottom, and where sea-weed, sea grass and benthic algae exist. In this study, the model indicates that oxygen-depleted water exists at the sea-bottom especially in summer mainly caused by an increase of oxygen consumption in the benthic system and a decrease of the vertical mixing water process. Furthermore, by comparing the case – with the tidal flat ecosystem model and the case without it, the effect of water purification of tidal flat estuaries was indicated. From the viewpoint of a short time scale, the tidal flat has the potential to restrict red tide (rapid increase of phytoplankton), and from the viewpoint of a long time scale, it restricts the sedimentation of detritus. Restricting the sedimentation prevents oxygen-depleted water occurring in the coastal marine system of Mikawa Bay.  相似文献   

Wide-Field Camera for Gravitational Microlensing Survey: MOA-cam2     

Toshifumi Yanagisawa  Yasushi Muraki  Yutaka Matsubara  Fumio Abe  Kimiaki Masuda  Sachiyo Noda  Takahiro Sumi  Yuji Kato  Mitsuaki Fujimoto  Shuji Sato  Ian Bond  Nicholas Rattenbury  Philip Yock  Pam Kilmartin  John Hearnshaw  Micheal Reid  Denis Sullivan  Brian Carter  Richard Dodd  Garry Nankivell  Noiman Rumsey  Morihiro Honda  Maki Sekiguchi  Masanori Yoshizawa  Takashi Nakamura  Humitaka Sato  Seiji Kabe  Makoto Kobayashi  Yoshiyuki Watase  Jun Jugaku  Toshiharu Saito  Barbel Koribalsky 《Experimental Astronomy》2000,10(4):519-535

We have constructed a large, mosaic CCD camera called MOA-cam2 which has 4096 × 6144-pixelsto search for gravitational microlensing events. MOA-cam2 has three4096 × 2048-pixel SITe CCD chips, which have a very high quantum efficiency (nearly 80% in the wave region 500 to 800 nm),and three buttable sides. We have placed the threechips side by side with 100 m dead space. MOA-cam2 has been installed on the 61 cm Boller and Chivens telescope of the MOA collaboration at the Mt. John University Observatory (MJUO) in NewZealand since July 1998. The field coverage is 0.92° × 1.38° per exposure. The technical details of MOA-cam2 and the first images obtained with the Boller and Chivens telescope are presented. MOA-cam2 introduces a second phase of research on gravitational microlensing by the MOA collaboration.  相似文献   

Floral changes in calcareous nannofossils and their paleoceanographic significance in the equatorial Pacific Ocean during the last 500 000 years     

Shun  Chiyonobu  Tokiyuki  Sato  Reika  Narikiyo  Makoto  Yamasaki 《Island Arc》2006,15(4):476-482

Abstract   The late Quaternary calcareous nannofossil assemblages from Ocean Drilling Program Holes 807A and 846B, located in the western and eastern equatorial Pacific Ocean, respectively, were analyzed to clarify changes in surface-water conditions during the last 500 000 years. The uppermost Quaternary sediments in both holes contain abundant nannofossils, and their assemblages are characterized by high species diversity. The absolute abundances of coccoliths (specimens/g) and relative numbers of small reticulofenestrids decreased drastically in both holes between 0.3 and 0.2 Ma, whereas the relative abundance of warm-water species and Florisphaera profunda increased suddenly at this time. These data indicate that upwelling around the western and eastern equatorial Pacific regions weakened after 0.2 Ma, which was caused by a decrease in trade-wind strength.  相似文献   

Damage process of pile foundation in liquefied ground during strong ground motion   总被引：1，自引：0，他引：1  

S. Miwa  T. Ikeda  T. Sato 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):325-336

The 1995 Hyogoken–Nambu earthquake caused severe liquefaction over wide areas of reclaimed land. Furthermore, the liquefaction induced large ground displacement in horizontal directions, which caused serious damage to foundations of structures. However, few analyses of steel pipe piles based on field investigation have so far been conducted to identify the causes and process of such damage. The authors conducted a soil–pile-structure interaction analysis by applying a multi-lumped-mass-spring model to a steel pipe pile foundation structure to evaluate the causes and process of its damage. The damage process analyzed in the time domain corresponded well with the results of detailed field investigation. It was found that a large bending moment beyond the ultimate plastic moment of the pile foundation structure was induced mainly by the large ground displacement caused by liquefaction before lateral spreading of the ground and that the displacement appeared during the accumulating process of the excess pore water pressure.  相似文献   

Cohesive Crack Analysis of Toughness Increase Due to Confining Pressure     

Kazushi Sato  Toshiyuki Hashida 《Pure and Applied Geophysics》2006,163(5-6):1059-1072

Apparent fracture toughness in Mode I of microcracking materials such as rocks under confining pressure is analyzed based on a cohesive crack model. In rocks, the apparent fracture toughness for crack propagation varies with the confining pressure. This study provides analytical solutions for the apparent fracture toughness using a cohesive crack model, which is a model for the fracture process zone. The problem analyzed in this study is a fluid-driven fracture of a two-dimensional crack with a cohesive zone under confining pressure. The size of the cohesive zone is assumed to be negligibly small in comparison to the crack length. The analyses are performed for two types of cohesive stress distribution, namely the constant cohesive stress (Dugdale model) and the linearly decreasing cohesive stress. Furthermore, the problem for a more general cohesive stress distribution is analyzed based on the fracture energy concept. The analytical solutions are confirmed by comparing them with the results of numerical computations performed using the body force method. The analytical solution suggests a substantial increase in the apparent fracture toughness due to increased confining pressures, even if the size of the fracture process zone is small.  相似文献