Size-fractionated primary production in the Kuroshio Extension and adjacent regions in spring     

Yuta Nishibe  Kazutaka Takahashi  Takuhei Shiozaki  Shigeho Kakehi  Hiroaki Saito  Ken Furuya 《Journal of Oceanography》2015,71(1):27-40

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The Mineral Adsorption and The Application of a Metamorphic Felsic Rock as Aggregate in Asphalt Pavements     

Lago  Larissa Neves  Casagrande  Michéle Dal Toé  da Conceição Ribeiro  Roberto Carlos  de Albuquerque e Silva  Ben-Hur 《Geotechnical and Geological Engineering》2022,40(3):1585-1595

Geotechnical and Geological Engineering - The aggregates consist approximately 85% of the total volume in asphalts pavements, and their properties influence directly their behavior. Therefore, it...  相似文献   

Degradation assessment of LYRA after 5 years on orbit - Technology Demonstration -     

A. BenMoussa  B. Giordanengo  S. Gissot  I. E. Dammasch  M. Dominique  J.-F. Hochedez  A. Soltani  N. Bourzgui  T. Saito  U. Schühle  A. Gottwald  U. Kroth  A. R. Jones 《Experimental Astronomy》2015,39(1):29-43

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Interannual and seasonal variation of the Huanghe (Yellow River) water discharge over the past 50 years: Connections to impacts from ENSO events and dams   总被引：4，自引：2，他引：2  

Houjie Wang  Zuosheng Yang  Yoshiki Saito  J. Paul Liu  Xiaoxia Sun   《Global and Planetary Change》2006,50(3-4):212-225

The Huanghe, the second largest river in China, is now under great pressure as a water resource. Using datasets of river water discharge, water consumption and regional precipitation for the past 50 years, we elucidate some connections between decreasing water discharges, global El Niño/Southern Oscillation (ENSO) events and anthropogenic impacts in the drainage basin. Global ENSO events, which directly affected the regional precipitation in the river basin, resulted in approximately 51% decrease in river water discharge to the sea. The degree of anthropogenic impacts on river water discharge is now as great as that of natural influences, accelerating the water losses in the hydrological cycle. The large dams and reservoirs regulated the water discharge and reduced the peak flows by storing the water in the flood season and releasing it in the dry season as needed for agricultural irrigation. Thus, as a result, large dams and reservoirs have shifted the seasonal distribution patterns of water discharge and water consumption and finally resulted in rapidly increasing water consumption. Meanwhile, the annual distribution pattern of water consumption also changed under the regulation of dams and reservoirs, indicating that the people living in the river basin consume the water more and more to suit actual agricultural schedule rather than depending upon natural pattern of annual precipitation. The combination of the increasing water consumption facilitated by the dams and reservoirs and the decreasing precipitation closely associated with the global ENSO events over the past half century has resulted in water scarcity in this world-famous river, as well as in a number of subsequent serious results for the river, delta and coastal ocean.  相似文献   

Numerical studies of vibratory pile driving     

I. M. Smith  P. To 《国际地质力学数值与分析法杂志》1988,12(5):513-531

The processes underlying pile installation by vibratory loading rather than impact loading are complex. However, numerical studies using simple models for soil behaviour do throw some light on the basic dynamic processes involved. As better soil models become widely used, quantitative analyses using the techniques described, or simplifications of them, should be feasible.  相似文献   

Primary proton spectrum around the knee deduced from the emulsion-chamber data obtained at Mts. Fuji and Kanbala     

J. Huang  N. Hotta  K. Kasahara  I. Ohta  S. Ozawa  T. Saito  M. Shibata  X. W. Xu  T. Yuda 《Astroparticle Physics》2003,18(6):637-648

We have done extensive Monte Carlo simulations using the new simulation codes of CORSIKA and COSMOS to compare with the gamma-family data obtained at Mts. Fuji (3750 m above sea level) and Kanbala (5500 m above sea level). Then, we estimated the primary proton and helium spectra around the knee energy region using a multiple-layered feed-forward neural network as a classifier of primary particle kind. The selection efficiency of proton-induced family events is estimated to be 82%. The flux value of protons at 2×10¹⁵ eV is (5.5±1.5)×10⁻¹⁴ (m⁻² s⁻¹ sr⁻¹ GeV⁻¹). The result suggests heavy-enriched primary composition around the knee region.  相似文献   

Fluctuations of electron precipitation to the dayside auroral zone modulated by compression and expansion of the magnetosphere     

T. Saito  F. Takahashi  A. Morioka  M. Kuwashima 《Planetary and Space Science》1974,22(6):939-953

Concurrent variations of CNA fluctuations and geomagnetic fluctuations are classified into Type 1 (substorm-type), Type 2 (Pc5-type), and Type 3 which is the object of the present study. Type 3 apparently has peculiar characteristics in that CNA fluctuations at a certain auroral-zone station show a pronounced positive correlation with magnetic fluctuations at distant low-latitude stations. The magnetic fluctuations of this type are identified to generalized Si which tends to take place much more frequently than the so-called Si. The CNA fluctuations of this type are found to take place on the dayside auroral zone only when preceded by a magnetic substorm on the night side. Considering the change of the growth rate of electron cyclotron instability and enhancement of pitch angle diffusion due to the change of magnetic field intensity, the following model is proposed to explain the occurrence mechanism of Type 3 concurrent variations. The CNA fluctuations take place only when two conditions are satisfied; generation of the accelerated electrons in association with substorm onset and modulation of the precipitation of the electrons by compression and expansion of the magnetosphere, in other words, by generalized Si.  相似文献   

A survey of possible impact structures on 25143 Itokawa     

Naru Hirata  Olivier S. Barnouin-Jha  Chikatoshi Honda  Ryosuke Nakamura  Hideaki Miyamoto  Sho Sasaki  Hirohide Demura  Akiko M. Nakamura  Tatsuhiro Michikami  Robert W. Gaskell  Jun Saito 《Icarus》2009,200(2):486-502

We determined the morphologies and dimensions of possible impact craters on the surface of Asteroid 25143 Itokawa from images taken by the Hayabusa spacecraft. Circular depressions, circular features with flat floors or convex floors, and circular features with smooth surfaces were identified as possible craters. The survey identified 38 candidates with widely varying morphologies including rough, smooth and saddle-shaped floors, a lack of raised rims and fresh material exposures. The average depth/diameter ratio was 0.08±0.03: these craters are very shallow relative to craters observed on other asteroids. These shallow craters are a result of (1) target curvature influencing the cratering process, (2) raised rim not being generated by this process, and (3) fines infilling the craters. As many of the crater candidates have an unusual appearance, we used a classification scheme that reflects the likelihood of an observed candidate's formation by a hypervelocity impact. We considered a variety of alternative interpretations while developing this scheme, including inherited features from a proto-Itokawa, spall scars created by the disruption of the proto-Itokawa, spall scars following the formation of a large crater on Itokawa itself, and apparent depressions due to random arrangements of boulders. The size-frequency distribution of the crater candidates was close to the empirical saturation line at the largest diameter, and then decline with decreasing diameter.  相似文献   

An analysis of heat waves in Serbia     

Miroslava Unkašević  Ivana Tošić 《Global and Planetary Change》2009,65(1-2):17-26

In this study, heat waves at three meteorological stations in Serbia were analyzed based on the daily maximum temperature during the summer (June, July and August). The warmest summers as regards heat wave duration and severity occurred within the periods 1951–1952, 1987–1998 (especially 1994) and 2000–2007. The longest heat waves were recorded in 1952, lasting 16 days in Smederevska Palanka and 21 days in Ni?, while in 1994 in Belgrade lasting 18 days. The summer of 1994 in Belgrade and Smederevska Palanka, and 2003 in Ni? were characterized with the highest number of consecutive tropical days (21 and 29, respectively).The autoregressive-moving-average models were applied to generate long series of the daily maximum temperature, from which the relative frequencies of heat waves were estimated. The relationships between the longest heat waves, and the circulation conditions were analyzed using the subjective Hess–Brezowsky catalogue of weather types.  相似文献   

The structure of monomeric and dimeric uranyl adsorption complexes on gibbsite: A combined DFT and EXAFS study     

Tatsuya Hattori  Takumi Saito  Andreas C. Scheinost  Shinya Nagasaki 《Geochimica et cosmochimica acta》2009,73(20):5975-1439

We investigated the structure of uranyl sorption complexes on gibbsite (pH 5.6-9.7) by two independent methods, density functional theory (DFT) calculations and extended X-ray absorption fine structure (EXAFS) spectroscopy at the U-L_III edge. To model the gibbsite surface with DFT, we tested two Al (hydr)oxide clusters, a dimer and a hexamer. Based on polarization, structure, and relaxation energies during geometry optimization, the hexamer cluster was found to be the more appropriate model. An additional advantage of the hexamer model is that it represents both edges and basal faces of gibbsite. The DFT calculations of (monomeric) uranyl sorption complexes show an energetic preference for the corner-sharing versus the edge-sharing configuration on gibbsite edges. The energy difference is so small, however, that possibly both surface species may coexist. In contrast to the edge sites, sorption to basal sites was energetically not favorable. EXAFS spectroscopy revealed in all investigated samples the same interatomic distances of the uranyl coordination environment (R_U-Oax ≈ 1.80 Å, R_U-Oeq ≈ 2.40 Å), and towards the gibbsite surface (R_U-O ≈ 2.87 Å, R_U-Al ≈ 3.38 Å). In addition, two U-U distances were observed, 3.92 Å at pH 9.7 and 4.30 Å at pH 5.6, both with coordination numbers of ∼1. The short U-U distance is close to that of the aqueous uranyl hydroxo dimer, UO₂(OH)₂, reported as 3.875 Å in the literature, but significantly longer than that of aqueous trimers (3.81-3.82 Å), suggesting sorption of uranyl dimers at alkaline pH. The longer U-U distance (4.30 Å) at acidic pH, however, is not in line with known aqueous uranyl polymer complexes. Based on the EXAFS findings we further refined dimeric surface complexes with DFT. We propose two structural models: in the acidic region, the observed long U-U distance can be explained with a distortion of the uranyl dimer to form both a corner-sharing and an edge-sharing linkage to neighboring Al octahedra, leading to R_U-U = 4.150 Å. In the alkaline region, a corner-sharing uranyl dimer complex is the most favorable. The U-O path at ∼2.87 Å in the EXAFS spectra arises from the oxygen atom linking two Al cations in corner-sharing arrangement. The adsorption structures obtained by DFT calculations are in good agreement with the structural parameters from EXAFS analysis: U-Al (3.394 Å), U-U (3.949 Å), and U-O (2.823 Å) for the alkaline pH model, and U-Al (3.279 Å), U-U (4.150 Å), and U-O (2.743 Å) for the acidic pH model. This work shows that by combining EXAFS and DFT, consistent structural models for uranyl sorption complexes can be obtained, which are relevant to predict the migration behavior of uranium at nuclear facilities.  相似文献