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51.
Estimating the Kuroshio Axis South of Japan Using Combination of Satellite Altimetry and Drifting Buoys 总被引:3,自引:4,他引:3
Daisuke Ambe Shiro Imawaki Hiroshi Uchida Kaoru Ichikawa 《Journal of Oceanography》2004,60(2):375-382
By tracking the locally strongest part of the sea-surface velocity field, which was obtained by integrating data of satellite
altimeters and surface drifting buoys, we extracted the Kuroshio axis south of Japan every 10 days from October 1992 to December
2000. The obtained axes clearly express the effect of the bottom topography; three modes were observed when the Kuroshio ran
over the Izu Ridge. The axis was very stable to the south of ‘Tosa-bae,’ off the Kii Channel. Mean current speed at the Kuroshio
axis gradually increased from 0.65 m/s south of Kyushu to 1.45 m/s off Enshu-nada.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
52.
Daisuke Tsumune Jun Nishioka Akifumi Shimamoto Shigenobu Takeda Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):111
The first iron (Fe) – fertilization experiment in the western North Pacific was carried out using SF6 to trace the Fe-fertilized water mass. A solution in 10,800 liters of seawater of 350 kg of Fe and 0.48 M of SF6 tracer was released into the mixed layer over a 8 × 10 km area. On the first underway transects through the patch after the Fe release, we observed a significant increase of dissolved Fe (ave. 2.89 nM). The fertilized patch was traced for 14 days by on-board SF6 analysis. A Lagrangian frame of reference was maintained by the use of a drogued GPS buoy released at the center of the patch. The patch moved westward at a rate of 6.8 km d−1. Mixed layer depth increased from 8.5 to 15 m during the experiment. Horizontal diffusivity was determined by the change of SF6 concentration in the patch. The horizontal diffusivity increased during the experiment. We evaluate here the fate of Fe in a Fe-fertilized patch using the dilution rate determined from sulphur hexafluoride (SF6) concentration. Dissolved Fe concentrations subsequently decreased rapidly to 0.15 nM on Day 13. However, the dissolved Fe half-life of 43 h was relatively longer than in previous Fe-enrichment studies, and we observed a larger increase of the centric diatom standing stock and corresponding drawdown of macro-nutrients and carbon dioxide than in the previous studies. The most important reason for the larger response was the phytoplankton species in the western North Pacific. In addition, the smaller diffusivity and shallower mixed layer were effective to sustain the higher dissolved Fe concentration compared to previous experiments. This might be one reason for the larger response of diatoms in SEEDS. 相似文献
53.
Simple monitoring method for precaution of landslides watching tilting and water contents on slopes surface 总被引:2,自引:2,他引:0
Taro Uchimura Ikuo Towhata Trinh Thi Lan Anh Jou Fukuda Carlos J. B. Bautista Lin Wang Ichiro Seko Taro Uchida Akira Matsuoka Yosuke Ito Yuichi Onda Sho Iwagami Min-Seok Kim Naoki Sakai 《Landslides》2010,7(3):351-357
A low-cost and simple monitoring method for early warning of landslides is proposed. To detect abnormal deformation of a slope, this method employs a tilt sensor in place of an extensometer on the slope surface. In order to examine the relevance of measuring rotation angle on a slope surface by tilt sensor, model tests were conducted, and rotation on the slope surface was observed together with slide displacement along the surface. The rotation data responded 30 min before failure in a model test, which could be useful as a signal for early warning. However, the behavior of rotation before failure varies from case to case, and thus, criteria to issue warning should be defined more carefully. For a model slope made of uniform loose sand, measurement of slide displacement along the slope surface is sensitive to failure at the toe, while the measurement of rotation on the slope surface is useful to detect the development of progressive failure upward along the slope. Wireless sensor units with microelectromechanical systems (MEMS) tilt sensor and volumetric water content sensor were also examined on a real slope in Kobe City, and a long-term monitoring was attempted. A simple but possible way to define the criteria of judgment to issue warning can be proposed based on combination of data obtained by the tilt sensors and volumetric water content sensors. 相似文献
54.
55.
This paper examines the possibility of using superconducting gravimeter (SG) observations without a tilt compensation system. SG data obtained at Syowa Station, Antarctica, were recorded without tilt compensation from April 5, 2001 to January 4, 2002, however, tilt signals were registered during this time period. A tilt correction was applied to gravity data from August 2, 2001 to January 4, 2002. After the tilt correction, errors of tidal parameters were dramatically reduced and tidal parameters themselves almost coincide with those from the same length of tilt-controlled gravity data recorded in 2000, when tilt compensation system was used. The noise level of the thermal leveler in the seismic band was also investigated. Averaged power spectra of gravity from 15 quiet days each in 2000 and 2001 recorded with and without the tilt compensation system, respectively, were compared. ‘Quiet’ in this case, means very low earthquake activity and calm wind conditions. No significant difference in the seismic band, except at the frequency of 2 mHz, was noticed. The difference at 2 mHz occurred because of room temperature variations caused by the water cooler, which cools down a compressor by automatically switching on and off. 相似文献
56.
Algebra, in particular commutative algebra, is applied here to provide a general unified solution to nonlinear systems of equations encountered in geodesy. Starting with the “Abelian group”, the “polynomial ring” is defined and used to form generators of ideals. By applying Buchberger or polynomial resultant algorithms, these generators are reduced to simple structures often comprising a univariate polynomial in one of the unknowns. The advantage of the proposed unified approach is that it provides exact solutions to geodetic nonlinear systems of equations without the traditional requirements of linearization, iterations or approximate starting values. The commutative algebraic approach therefore alleviates the need for isolated exact solutions to various geodetic nonlinear systems of equations. The procedure is applied to GPS meteorology to compute refraction angles, and Helmert’s one-to-one mapping of topographical points onto the reference ellipsoid. 相似文献
57.
Norimasa Nishiyama Robert Paul Rapp Tetsuo Irifune Takeshi Sanehira Daisuke Yamazaki Ken-ichi Funakoshi 《Physics and Chemistry of Minerals》2005,32(8-9):627-637
In situ X-ray diffraction measurements of KAlSi3O8-hollandite (K-hollandite) were performed at pressures of 15–27 GPa and temperatures of 300–1,800 K using a Kawai-type apparatus. Unit-cell volumes obtained at various pressure and temperature conditions in a series of measurements were fitted to the high-temperature Birch-Murnaghan equation of state and a complete set of thermoelastic parameters was obtained with an assumed K′300,0=4. The determined parameters are V 300,0=237.6(2) Å3, K 300,0=183(3) GPa, (?K T,0/?T) P =?0.033(2) GPa K?1, a 0=3.32(5)×10?5 K?1, and b 0=1.09(1)×10?8 K?2, where a 0 and b 0 are coefficients describing the zero-pressure thermal expansion: α T,0 = a 0 + b 0 T. We observed broadening and splitting of diffraction peaks of K-hollandite at pressures of 20–23 GPa and temperatures of 300–1,000 K. We attribute this to the phase transitions from hollandite to hollandite II that is an unquenchable high-pressure phase recently found. We determined the phase boundary to be P (GPa)=16.6 + 0.007 T (K). Using the equation of state parameters of K-hollandite determined in the present study, we calculated a density profile of a hypothetical continental crust (HCC), which consists only of K-hollandite, majorite garnet, and stishovite with 1:1:1 ratio in volume. Density of HCC is higher than the surrounding mantle by about 0.2 g cm?3 in the mantle transition zone while this relation is reversed below 660-km depth and HCC becomes less dense than the surrounding mantle by about 0.15 g cm?3 in the uppermost lower mantle. Thus the 660-km seismic discontinuity can be a barrier to prevent the transportation of subducted continental crust materials to the lower mantle and the subducted continental crust may reside at the bottom of the mantle transition zone. 相似文献
58.
59.
Daisuke Yamazaki Eiji Ito Yoshinori Tange Takashi Yoshino Shuangmeng Zhai Hiroshi Fukui Anton Shatskiy Tomoo Katsura Ken-ichi Funakoshi 《Physics and Chemistry of Minerals》2007,34(4):269-273
In situ X-ray observations of the phase transition from ilmenite to perovskite structure in MnGeO3 were carried out in a Kawai-type high-pressure apparatus interfaced with synchrotron radiation. The phase boundary between
the ilmenite and perovskite structures in the temperature range of 700–1,400°C was determined to be P (GPa) = 16.5(±0.6) − 0.0034(±0.0006)T (°C) based on Anderson’s gold pressure scale. The Clapeyron slope, dP/dT, determined in this study is consistent with that for the transition boundary between the ilmenite and the perovskite structure
in MgSiO3. 相似文献
60.
Daisuke?Takagi Hiroaki?SatoEmail author Mitsuhiro?Nakagawa 《Contributions to Mineralogy and Petrology》2005,149(5):527-540
We conducted melting experiments on a low-alkali tholeiite (SiO2 ~52 wt%, MgO ~6.5 wt%, CaO/Na2O~4.4, Al2O3/SiO2 ~0.33) under both H2O-undersaturated and H2O-saturated conditions to investigate the effect of H2O on the Ca–Na partitioning between plagioclase and melt. Experiments were performed in the temperature and pressure ranges of 1,000–1,300°C and 1–5 kbar, respectively, with varying H2O contents of 0–12wt%. Redox condition was 0–2 log unit above NNO (nickel–nickel oxide) buffer. Temperature-bulk H2O diagrams for the low-alkali tholeiite are constructed at 1, 2, and 5 kbar, and compositions of near-liquidus plagioclase and coexisting melt are determined. To exclude the effect of melt composition (CaO/Na2O and Al2O3/SiO2 ratios) on plagioclase composition and to reveal the effect of H2O on An (=100×Ca/(Ca+Na)) content and
(=(Ca/Na)pl/(Ca/Na)melt), we focused on the composition of near-liquidus plagioclases which crystallized from melts with nearly constant CaO/Na2O and Al2O3/SiO2 ratios. Our experimental results show that, at each experimental pressure, An content of the near-liquidus plagioclase and the KDCa-Na almost linearly increases as H2O content in melt increases. Each of the An content and the
variations in a low-alkali tholeiitic system (CaO/Na2O~4.0–4.5, Al2O3/SiO2 ~0.27–0.33) can be described by one equation using temperature, pressure, and melt H2O content as parameters. An content and
of liquidus plagioclase increases with increasing melt H2O and with decreasing pressure, elucidating that nearly H2O-saturated conditions of 2–3 kbar is optimal for the crystallization of the most An-rich plagioclase (>An88). We suggest this pressure condition of 2–3 kbar, corresponding to depth of 7–11 km, plays an important role for the origin of An-rich plagioclase in H2O-rich low-alkali tholeiite. At pressures more than ca. 4 kbar, crystallization of liquidus Ca-rich clinopyroxene decreases the CaO/Na2O ratio of liquid, thus prohibiting the crystallization of high-An plagioclase from hydrous tholeiite. 相似文献