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排序方式: 共有170条查询结果,搜索用时 31 毫秒
11.
Yoshihisa?MinoEmail author Chiho?Sukigara Makio?C.?Honda Hajime?Kawakami Kazuhiko?Matsumoto Masahide?Wakita Minoru?Kitamura Tetsuichi?Fujiki Kosei?Sasaoka Osamu?Abe Jan?Kaiser Toshiro?Saino 《Journal of Oceanography》2016,72(6):819-836
Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ 15N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ 15N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ 15N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ 15N(SUS) signature was reflected by δ 15N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ 15N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ 15N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ 15N(DST) vs. PP regression to δ 15N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully. 相似文献
12.
Conversion factors are useful for attenuation and damage estimation relationships. These factors among different definitions of peaks (i.e. larger, average and resultant) for peak ground motion indices and acceleration response spectrum were investigated. A large number of horizontal acceleration records recorded at 76 free-field sites of the Japan Meteorological Agency were used in this study. Two orthogonal horizontal components were combined in the time domain to get the maximum resultant peak ground motion indices and acceleration response spectrum in the horizontal plane. From the analysis, the means of the larger/resultant ratio were found to be 0·934 for acceleration, 0·926 for velocity, and 0·913 for displacement. A similar decreasing trend was observed for the means of the average/resultant ratio of the ground motion indices and acceleration response spectrum. The directivity of peak ground motion indices was also examined. It was found that the peak ground motion is more likely to occur in the transverse direction than in other directions. This trend is more prominent in the long-period contents of ground motion. 相似文献
13.
Kazutaka Yamaoka Yoshihiro Ueda Hajime Inoue Fumiaki Nagase Ken Ebisawa Taro Kotani Yasuo Tanaka 《Astrophysics and Space Science》2001,276(1):19-22
We summarize the ASCA observations of the two Galactic superluminal sources GRO J1655–40 and GRS 1915+105, focusing on theabsorption line features.The high spectroscopic capability of ASCA enabled us to detectiron-K absorption line features from both objects. This is direct evidence for the presence of highly ionized plasma in a non-spherical configuration around a black hole, and is considered to be a unique signature of superluminal jet systems. The candidate of the line-absorber would be a part of an accretion disk at a distance of 109-11 cm from the central X-ray source. 相似文献
14.
Soil amplification characteristics of earthquake ground motion were investigated in terms of peak ground acceleration and transfer function based on the Chiba array observation records. The amplification of peak ground acceleration occurred mostly at the top soft layer and was similar for the three components. The effects of non-linear response of soil deposits on the transfer function were examined. Transfer functions calculated by ensemble average were close for the two horizontal components while those obtained from a smoothing operation were generally different. Both the transfer functions from the ensemble average and the smoothing operation underestimated the gain factor around the natural frequencies. A two-step smoothing procedure was proposed and a rotary spectrum was used to improve the estimation of the transfer function. Microtremors were observed at the locations of the boreholes where seismometers are buried. The power spectrum and spatial coherency of the microtremors were compared with those of the earthquake ground motion. Emphasis was placed on the wavetypes which dominated the peaks in the power spectra. 相似文献
15.
Array observation is an efficient tool to investigate various characteristics of earthquake ground motion. However, seismographs used in arrays may involve unexpected errors in their orientations. Methods of orientation error estimation were developed in three-dimensional space by comparing recorded ground motions at a reference point with those at a checking point. A maximum cross-correlation method and a maximum coherence method were proposed and their accuracy was demonstrated. The earthquake ground motions recorded in the Chiba array and in two other arrays were used in numerical examples. Non-trivial orientation errors were detected for all these arrays. The cross-correlation coefficients and the coherence values between two points increased significantly by correcting the estimated orientation errors. 相似文献
16.
Miscellaneous information 相似文献
17.
A shock-wave heating model is one of the possible models for chondrule formation. We examine, within the framework of a shock-wave heating model, the effects of evaporation on the heating of chondrule precursor particles and the stability of their molten state in the postshock flow. We numerically simulate the heating process in the flow taking into account evaporation. We find that the melting criterion and the minimum radius criterion do not change significantly. However, if the latent heat cooling due to the evaporation dominates the radiative cooling from the precursor particle, the peak temperature of the precursor particle is suppressed by a few hundred Kelvins. We also find that the total gas pressure (ram plus static) acting on the precursor particle exceeds the vapor pressure of the molten precursor particle. Therefore, it is possible to form chondrules in the shock-wave heating model if the precursor temperature increases up to the melting point. 相似文献
18.
Heqing DU Hajime MIWA 《国际泥沙研究》2006,21(1):1-12
Alternate bars have the property that they migrate downstream whenever floods occur. However, in meander channels whose bend angles are larger than a critical value, the migration of bars can be suppressed, and the positions of bank erosion and flood attack also will be steady. In this study, the bed morphology in flume channels with bends of various lengths and angles is investigated at various flow discharges, and the relation of bed morphology to surface flow is investigated in detail using fluid measuring software. An effort is made to obtain guidelines for the plane shape design of meander channels. Based on the experimental results of bed topography and measurement of surface flow direction and velocity distribution, from the viewpoint of bank erosion and the concentration and dispersion of flood flow the most suitable plane shape for meandering channels is suggested through which the migration of alternate bars is suppressed. 相似文献
19.
Abstract: Low sulphidation epithermal Au-Ag deposits constitute a major exploration target for many mining companies worldwide. These deposits are commonly characterized by quartz vein systems which formed at temperatures often in the range 150–250°C giving rise to major alteration halos. Accompanying mineralization and associated alteration is the destruction and redistribution of magnetite in the host rocks and the formation of various K-bearing minerals such as adularia, illite and alunite. These alteration halos can often cover an area of at least several square kilometres and as such have the potential to be detected during reconnaissance geological surveys utilizing high resolution airborne aeromagnetic and radiometric sensors.
Analysis of airborne magnetic and radiometric data recently acquired over the Hokusatsu Region of SW Kyushu indicates that major low sulphidation epithermal Au-Ag deposits are characterized by several distinct geophysical features varying with the degree of post-mineralization cover and level of erosion. Several deposits coincide with extensive magnetic "flat" and high radiometric K–counts. In addition, several workers have shown that a very close association exists between Bouguer gravity highs and epithermal Au mineralization in the Hokusatsu Region. The combined use of areomagnetics, radiometrics and gravity data therefore provides an exceptionally effective approach to exploration for low sulphidation epithermal Au–Ag deposits in the Hokusatsu Region of Japan. 相似文献
Analysis of airborne magnetic and radiometric data recently acquired over the Hokusatsu Region of SW Kyushu indicates that major low sulphidation epithermal Au-Ag deposits are characterized by several distinct geophysical features varying with the degree of post-mineralization cover and level of erosion. Several deposits coincide with extensive magnetic "flat" and high radiometric K–counts. In addition, several workers have shown that a very close association exists between Bouguer gravity highs and epithermal Au mineralization in the Hokusatsu Region. The combined use of areomagnetics, radiometrics and gravity data therefore provides an exceptionally effective approach to exploration for low sulphidation epithermal Au–Ag deposits in the Hokusatsu Region of Japan. 相似文献
20.
Hedonic approaches based on spatial econometrics and spatial statistics: application to evaluation of project benefits 总被引:1,自引:0,他引:1
This study discusses the theoretical foundation of the application of spatial hedonic approaches—the hedonic approach employing
spatial econometrics or/and spatial statistics—to benefits evaluation. The study highlights the limitations of the spatial
econometrics approach since it uses a spatial weight matrix that is not employed by the spatial statistics approach. Further,
the study presents empirical analyses by applying the Spatial Autoregressive Error Model (SAEM), which is based on the spatial
econometrics approach, and the Spatial Process Model (SPM), which is based on the spatial statistics approach. SPMs are conducted
based on both isotropy and anisotropy and applied to different mesh sizes. The empirical analysis reveals that the estimated
benefits are quite different, especially between isotropic and anisotropic SPM and between isotropic SPM and SAEM; the estimated
benefits are similar for SAEM and anisotropic SPM. The study demonstrates that the mesh size does not affect the estimated
amount of benefits. Finally, the study provides a confidence interval for the estimated benefits and raises an issue with
regard to benefit evaluation. 相似文献