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61.
Misao Sasaki 《Journal of Astrophysics and Astronomy》1999,20(3-4):281-289
In this talk, I review an analytic method for calculating gravitational radiation from a small mass particle orbiting a massive
black hole. This method allows a systematic evalutation of the gravitational radiation to a very high order in post-Newtonian
expansion, hence gives us useful information on the evolution of coalescing compact binary stars. 相似文献
62.
Tai Sasaki Naro Hashimoto Takayuki Nakato Tomonari Shiraishi Kazuaki Yajima Tomoyuki Hishiya 《Engineering Geology》1998,49(3-4):337-343
As a preliminary step for predicting groundwater flow in a plateau 30–50 m above sea level, a model for three-dimensional analysis of groundwater flow was formulated and its validity was verified. The plateau consists of Neogene sedimentary rocks and a Quaternary deposit. Most of the groundwater originates in precipitation, with the groundwater table lying in the Quaternary deposit. Steady-state analysis was conducted by using the finite element method. The results of pore-water pressure measurement and water examination were useful in verifying the validity of the model. In constructing the model, reducing the hydraulic conductivity according to the depth on the basis of the results of the actual measurement was important. 相似文献
63.
Akihiro Shiomoto Katsuyuki Sasaki Toru Shimoda Satsuki Matsumura 《Journal of Oceanography》1994,50(5):515-529
The maximum uptake rate (max) and affinity constant (K
s) for nitrate and ammonium were estimated in the surface water of offshore Oyashio in May (spring) and September (summer), 1990. The average max/Chl.a for ammonium was 2.1 times larger than that of nitrate in both seasons. The average max/Chl.a for both nitrogens were 3.5 times larger in summer than in spring. Water temperature and size composition of phytoplankton population were related to the seasonal difference in the max/Chl.a. Phytoplankton population showed high affinity for both nitrogens in the spring and summer. In addition, the contribution of new production to total production was estimated by max[max–No3/(max–NO3+max–NH4)]. The spring value was in the range of 0.26 to 0.45 (mean±SD=0.35±0.092), and the values in spring bloom were especially a little over 0.4. The summer value was in the range of 0.30 to 0.37 (0.34±0.04). 相似文献
64.
Tsuneo?OnoEmail author Hiromi?Kasai Takashi?Midorikawa Yusuke?Takatani Kazuhiro?Saito Masao?Ishii Yutaka?W.?Watanabe Katsuyuki?Sasaki 《Journal of Oceanography》2005,61(6):1075-1087
Eight-year observation results of DIC from 1996 to 2003 in the Oyashio region have been analyzed to obtain a climatological
view of its seasonal variation and interannual variation. Data of DIC obtained by several institutes are synthesized to give
a dataset with an uncertainty lower than 5 μmol/kg. The obtained climatology of NDIC seasonal variation in the Oyashio mixed layer shows a seasonal amplitude of 176 μmol/kg, with a maximum in January and a minimum in September. These features closely resemble those observed in the southern
half of the western subarctic North Pacific (WSNP) including Station KNOT, although the timing of the NDIC maximum is slightly
advanced in the case of the Oyashio. Analysis using a quasi-conservative tracer Cp0 (NDIC - 106NP) shows that among 176 μmol/kg of NDIC seasonal variation, only 16 μmol/kg is attributed to hydrographic processes while the remaining 160 μmol/kg is attributed to biological processes. The Cp0 value in the Oyashio mixed layer also resembles that of the WSNP mixed
layer during the months May to November, suggesting further resemblance of the Oyashio water mass to that of WSNP in terms
of carbon dynamics. The present results also suggest that a single data obtained in Oyashio mixed layer contains 30 μmol/kg of potential uncertainty for the representativity of this region, which leads to a note about a need to treat with
caution results obtained by a single observation in this region. 相似文献
65.
Sinking particulate matter were obtained from twelve depths using free-drifting sediment trap arrays which were deployed in the upper 2,000 m water column of the Izu Trench, northwest Pacific Ocean. The largest flux of 146 mgC m–2 day–1 was observed at 150 m depth. The flux generally decreased with depth below the maximum, however, minor flux peaks occurred at 1,000 and 1,250 m depth (>30 mgC m–2 day–1). Sinking large particles (>100 µm) were composed of fecal pellets typical of crustaceans, macroscopic aggregates, and planktonic organisms and their fragments. Three major components constituted 19%, 20% and 29%, respectively, of the total carbon flux (averaged from the fluxes at five depths; 50, 100, 150, 1,000 and 2,000 m). Among them, fecal pellet flux and large organism flux were well correlated with the total flux. The close correspondence between the fecal flux and the total carbon flux suggests that the latter is derived from a group of variables including other biogenic matter, among which fecal pellet is one of the leading factors controlling total flux, though the latter is only a minor covariable in quantity. Vertical flux profiles of fecal pellets and their internal constituents revealed some new inputs of feces occurring through the water column. This phenomenon implies that downward transportation of organic material is characterized by feeding and egestion activities of zooplankton, including overlapping processes of sinking and dispersion of large fecal particles and repackaging of dispersed small particles. 相似文献
66.
Alexandre Forest Simon Bélanger Makoto Sampei Hiroshi Sasaki Catherine Lalande Louis Fortier 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(1):125-142
Surface concentrations and vertical fluxes of particulate organic carbon (POC) were assessed in the Amundsen Gulf (southeastern Beaufort Sea, Arctic Ocean) over the years 2004 to 2006 by using ocean color remote-sensing imagery and sequential sediment traps moored over the ca. 400 m isobath. Environmental conditions (sea ice, wind) and oceanographic variables (temperature, salinity, fluorescence and currents) were investigated to explain the variability of POC data. Annual downward POC fluxes in 2004, 2005 and 2006 cumulated, respectively, to 3.3, 4.2 and 6.0 g C m?2 yr?1 at ~100 m depth, and to 1.3, 2.2 and 3.3 g C m?2 yr?1 at ~210 m depth. The fraction of settling POC attributable to autochthonous processes occurring at or next to ice break-up was estimated to be 75–84% of the 100 m annual fluxes and to be 61–75% of the 210 m fluxes. Over the three ice-reduced seasons, distinct scenarios between ice conditions, surface POC pools and vertical POC export at 100 m were identified: (1) in 2004, despite a normal ice break-up, a weak primary production was measured and low vertical fluxes were collected as old ice moved across the region; (2) in 2005, a lengthened ice-free period allowed an extended season of surface POC production near-shore, while an intermediate increase of vertical fluxes was recorded offshore; and (3) in 2006, a late ice melt gave rise to a pulsed ice edge bloom and to large vertical fluxes also associated with extra ice-flushed material. Linear regressions of vertical POC fluxes against satellite-derived surface POC concentrations suggested that the pelagic POC retention in the upper 100 m of the Amundsen Gulf ranged from ca. 70% to 90% depending on the timing of ice cover melt. Regardless of the inter-annual variability, the estimated fraction of the surface POC reservoir reaching the 210 m water depth was reduced to ~5%. Therefore, as the Arctic Ocean warms up, our results support the expectation that the increasing extent of the seasonal ice zone will promote the POC pathways that benefit pelagic webs rather than benthic communities. 相似文献
67.
The proposals made for improving ground resolution in satellite microwave radiometry primarily seek to sharpen the main beam and refine hardware. However, deformation and changes in electromagnetic characteristics with scanning still significantly affect the antenna patterns of large-aperture antennas. This paper proposes an advanced method with two improvements. The first improvement is related to the method used to obtain a point spreading function (PSF) filter at every spot of interest in the scanning footprint. The method estimates only a typical PSF of the footprint just below the satellite orbit and applies rotation by the angular change that occurs as the footprint moves and rotates with scanning. The second improvement is to introduce a projection onto convex sets (POCS) method into the iterative calculation to solve the inverse problem and to find the most likely estimate of ground information. Two pieces of a priori information are also introduced in the iteration to achieve rapid convergence and reasonable estimation: The brightness temperature of the ground surface is 1) smooth and 2) nonnegative. Correlations between estimated results are also taken between neighboring footprints after retrieval, and convergence is easily attained in the iteration. As no practical satellite data were available, an observational simulation was used as a case study at the lowest frequency (6.9 GHz), which has the poorest resolution. In this case study, ice margins were clearly retrieved by the algorithm when ice floes were 50 km or more apart. Irregularities like ringing, unreasonable undulation, or unreasonable values have occasionally appeared with the current method, but are absent with the proposed improved inversion method used in combination with a POCS method. 相似文献
68.
R. Feldmann C. M. Carollo C. Porciani S. J. Lilly P. Capak Y. Taniguchi O. Le Fèvre A. Renzini N. Scoville M. Ajiki H. Aussel T. Contini H. McCracken B. Mobasher T. Murayama D. Sanders S. Sasaki C. Scarlata M. Scodeggio Y. Shioya J. Silverman M. Takahashi D. Thompson G. Zamorani 《Monthly notices of the Royal Astronomical Society》2006,372(2):565-577
69.
L. Fedele F. Raia M. Sasaki T. Sawaki M. Tarzia M. Sasada 《Mineralogy and Petrology》2005,84(3-4):189-213
Summary The hydrothermal evolution of the Sengan geothermal area, Northern Honshu, was studied using fluid inclusion microthermometry.
Sengan is one of the most active geothermal areas in Japan, and it is dominated by andesitic to dacitic volcanic rocks of
Pliocene and Quaternary age. Fluid inclusions were studied in hydrothermal minerals (quartz, calcite, anhydrite, wairakite)
and in fractured igneous quartz phenocrysts from core samples retrieved from five geothermal exploration wells, which penetrated
Quaternary and Tertiary formations, and intrusive rocks in or around the calderas. A caldera-hosted hydrothermal system was
heated by a shallow intrusion, which produced hypersaline fluids. During the early stages some heterogeneity in fluid composition
occurred, but during peak activity of the hydrothermal system, the fluid was dominantly low-salinity, and most likely of meteoric
origin. We have reconstructed, by means of fluid inclusion studies, the structure of an extinct hydrothermal system in a Pliocene
caldera filled with ignimbrites, and of an active hydrothermal system which is now being heated under the northern slope of
Yakeyama volcano. Based on inclusion data, the aqueous fluids that circulated in the hydrothermal system ranged from very
low saline (0–7 wt.% NaCl equiv.) to hypersaline (up to 60 wt.% NaCl equiv.), with temperatures ranging from 130 to 400 °C. 相似文献
70.