排序方式： 共有28条查询结果，搜索用时 265 毫秒
1.
Size-Fractionated Primary Production Estimated by a Two-Phytoplankton Community Model Applicable to Ocean Color Remote Sensing 总被引：3，自引：0，他引：3
In order to estimate primary production from ocean color satellite data using the Vertical Generalized Production Model (VGPM; Behrenfeld and Falkowski, 1997), we propose a two-phytoplankton community model. This model is based on the two assumptions that changes in chlorophyll concentration result from changes of large-sized phytoplankton abundance, and chlorophyll specific productivity of phytoplankton tends to be inversely proportional to phytoplankton size. Based on the analysis of primary production data, P
opt
B
, which was one parameter in the VGPM, was modeled as a function of sea surface temperature and sea surface chlorophyll concentration. The two-phytoplankton community model incorporated into the VGPM gave good estimates in a relatively high productive area. Size-fractionated primary production was estimated by the two-phytoplankton community model, and P
opt
B
of small-sized phytoplankton was 4.5 times that of large-sized phytoplankton. This result fell into the ranges observed during field studies. 相似文献
2.
Mean slope-angle frequency distribution and size frequency distribution of landslide masses in Higashikubiki area, Japan 总被引：1，自引：0，他引：1
Landslide mass size frequency distributions and mean slope-angle frequency distributions were calculated for slump, slide, and creep type landslides in the Higashikubiki area. Mean slope-angle frequency distributions closely approximated Weibull distributions. Size frequency distributions show power-law dependencies. Both can be explained by modeling landslides as linked uniform blocks in tensile force. Power coefficients for size frequency distributions were 2.01–2.32 (approximation to power functions) or 2.10–2.24 (approximation to Pareto distributions). 相似文献
3.
Ken Goto Takahiro Itoh Takahiko Nagayama Rei Utsunomiya Daizo Tsutsumi Takahisa Mizuyama 《山地科学学报》2016,13(2):369-376
Bedload governs riverbed channel variations and morphology, it is necessary to determine bedload discharge through an arbitrary cross section in a mountain river. A new system with submerged load cells has been developed to directly measure bedload discharge. The system consists of: (1) an iron box which is 1 m long, 0.5 m wide and 0.1 m in depth, (2) two submerged load cells 0.7 m apart, (3) a pressure sensor and, (4) an electromagnetic velocity meter. This system has been designed to exclude the effect of the hydraulic pressure of water on direct measurements of bedload particle weight. Initial tests in a laboratory were conducted to examine the accuracy of measurements with the system under aerial conditions. The system has been installed in the supercritical flume in Ashi-arai-dani River of the Hodaka Sedimentation Observatory of the Disaster Prevention Research Institute (DPRI) of Kyoto University to obtain bedload discharge under natural conditions. Flume tests were conducted in this channel by artificial supply of uniform sediment particles of several grain sizes. The average velocity of the sediment particles near the bed was estimated using cross-correlation functions for weight waves obtained by the two load cells. Bedload discharge calculations were based on time integration of the product of sediment velocity and sediment weight obtained by the two load cells. This study clarifies the reasons why bedload measurements are difficult, and provides some solutions using the monitoring systems with submerged load cells through the field measurements. Additionally, the applicability of bedload measurement with the submerged load cells is explained based on experimental artificial sediment supply data. 相似文献
4.
The effect of southward or northward changes in the interplanetary magnetic field is examined statistically in the nightside magnetosphere over the range of 6.6 to 80R
E from the Earth. After southward changes, the deformation of the magnetosphere toward a greater antisunward extension of field lines occurs at 6.6R
E with 10 min delay and spreads down the tail to 80R
E in 30 min. Around the onset of the field-line collapse that occurs 1–2 hr later, the southwarddirected field is observed briefly in the distant tail. The effect of northward changes could not be recognized in the lobe region of the tail. 相似文献
5.
Nassef M Tawaratsumita T Oba Y Satone H Nakayama K Shimasaki Y Honjo T Oshima Y 《Marine pollution bulletin》2011,62(2):412-414
In this study, individual Japanese flounder were intraperitoneally injected with 2 μg tributyltin-d27 (TBT-d27) fish−1. Blood samples were collected on day 7 after injection. TBT-binding protein types 1 and 2 (TBT-bp1, -bp2) in the blood serum were quantified by western blotting analysis. As a result, the concentration of TBT-bp2 in TBT-d27 treated group increased to 220% of that in the solvent control, whereas the TBT-bp1 concentration decreased to 65% of that in the solvent control. Additionally, a positive relationship between the concentrations of TBT-bp2 and TBT was observed in blood sera of wild and cultured flounder. We suggest that TBT-bp2 is produced in response to TBT exposure and may play an important role in fish physiology. 相似文献
6.
Aerodynamic Parameters of Regular Arrays of Rectangular Blocks with Various Geometries 总被引：8，自引：8，他引：0
The aerodynamic effects of various configurations of an urban array were investigated in a wind-tunnel experiment. Three aerodynamic
parameters characterising arrays—the drag coefficient (C
d
), roughness length (z
o) and displacement height (d)—are used for analysis. C
d
is based on the direct measurement of the total surface shear using a floating element, and the other two parameters are
estimated by logarithmic fitting of the measured wind profile and predetermined total drag force. The configurations of 63
arrays used for measurement were designed to estimate the effects of layout, wind direction and the height variability of
the blocks on these parameters for various roughness packing densities. The results are summarised as follows: (1) The estimated
C
d
and z
o of the staggered arrays peak against the plan area index (λ
p
) and frontal area index (λ
f
), in contrast with values for the square arrays, which are less sensitive to λ
p
and λ
f
. In addition, the square arrays with a wind direction of 45° have a considerably larger C
d
, and the wind direction increases z
o/H by up to a factor of 2. (2) The effect of the non-uniformity of roughness height on z
o is more remarkable when λ
f
exceeds 20%, and the discrepancy in z
o is particularly remarkable and exceeds 200%. (3) The effect of the layout of tall blocks on C
d
is stronger than that of short blocks. These results indicate that the effects of both wind direction and the non-uniformity
of the heights of buildings on urban aerodynamic parameters vary greatly with λ
p
and λ
f
; hence, these effects should be taken into account by considering the roughness packing density. 相似文献
7.
8.
Sayaka Sogawa Takashi Kidachi Masahumi Nagayama Tadafumi Ichikawa Kiyotaka Hidaka Tsuneo Ono Yugo Shimizu 《Journal of Oceanography》2017,73(5):603-622
A continuous survey examined short-term variations in the zooplankton community and physical ocean environment from the northeastern Izu Islands to Boso Peninsula in Japan. High copepod abundance and small upwellings in the surface layer and salinity minimum layer in the subsurface were observed on the north side of coastal fronts in the westernmost transect, moving southward as the Kuroshio Current left the Boso Peninsula. Thus, the salinity minimum layer might be a key factor forming upwelling and the fronts, leading to large abundance of coastal copepods off the northeastern Izu Islands. A community structure analysis of calanoid copepods revealed an intermediate belt assemblage between coastal and offshore (Kuroshio) assemblages. Copepod abundance was remarkably low and Ctenocalanus vanus dominated (nearly 37%) in the intermediate belt zone, indicating that C. vanus has a relatively high tolerance to adverse environments for calanoid copepods. As the Kuroshio Current left the Boso Peninsula, the coastal assemblage expanded in the same direction, and the intermediate belt assemblage off the northeastern Izu Islands disappeared. The largest population of Calanus sinicus was found along the two western transects off the northeastern Izu Islands (>1000 m depth), which was assumed to be transported from Sagami Bay and advanced southwestward while growing from copepodite stages CIII to CV. Larvae of C. sinicus would be an important food for fish larvae in addition to Paracalanus parvus s.l., the numerically dominant species in the coastal assemblage, and C. vanus under the adverse conditions for coastal copepods. 相似文献
9.
Located off the Pacific coast of central Tohoku (NE Japan), the Ishinomaki slope channel (ISC) provides an excellent opportunity to study a structure-controlled intraslope channel and downslope sedimentation along the active margin. The seismic reflection data across ISC show an extensive basal surface and overlying channel complexes between the basement structures of the Abukuma ridge to the south and Kitakami massif to the north, indicating that the formation of the intraslope basin, channelization of ISC and sedimentation of the downstream channel-lobe transition zone (CLTZ) are very likely to be structure-controlled. The oblique channel stacking pattern, faulting of the seafloor and subsurface Abukuma ridge in the upper and lower domains of ISC, collectively suggest that ISC has migrated northward and is currently under the influence of active compression. Differences in styles of accommodation space between the upper and lower domains of ISC suggest that differential subsidence occurred along the strike-slip tectonic line. Based on the regional strike-slip tectonic line, we propose that a Kitakami-Abukuma ridge existed before the formation of ISC. The strike-slip faulting divided the Kitakami-Abukuma ridge into the Kitakami massif to the north and the Abukuma ridge to the south, and an intervening fault trough as the precursor of the intraslope basin and ISC. As the subduction of the Pacific Plate and associated compressional events continued, the Abukuma ridge was reactivated to narrow the intraslope basin into a confined channel. Located near the epicentre of the devastating 2011 Tohoku earthquake event, the ISC, downstream CLTZ and underlying intraslope basin provide information on active basement structure and the evolving sediment routing system on the tectonically active margin. 相似文献
10.
Chiaki Hikage Kazuya Koyama Takahiko Matsubara Tomo Takahashi Masahide Yamaguchi 《Monthly notices of the Royal Astronomical Society》2009,398(4):2188-2198
We study the effect of primordial isocurvature perturbations on non-Gaussian properties of cosmic microwave background (CMB) temperature anisotropies. We consider generic forms of the non-linearity of isocurvature perturbations which can be applied to a wide range of theoretical models. We derive analytical expressions for the bispectrum and the Minkowski Functionals for CMB temperature fluctuations to describe the non-Gaussianity from isocurvature perturbations. We find that the isocurvature non-Gaussianity in the quadratic isocurvature model, where the isocurvature perturbation S is written as a quadratic function of the Gaussian variable σ, S =σ2 −〈σ2 〉 , can give the same signal-to-noise ratio as f NL = 30 even if we impose the current observational limit on the fraction of isocurvature perturbations contained in the primordial power spectrum α. We give constraints on isocurvature non-Gaussianity from Minkowski Functionals using the Wilkinson Microwave Anisotropy Probe ( WMAP ) 5-year data. We do not find a significant signal of isocurvature non-Gaussianity. For the quadratic isocurvature model, we obtain a stringent upper limit on the isocurvature fraction α < 0.070 (95 per cent CL) for a scale-invariant spectrum which is comparable to the limit obtained from the power spectrum. 相似文献