Bio-Optical Relationship of Case I Waters: The Difference Between the Low- and Mid-Latitude Waters and the Southern Ocean     

Toru Hirawake  Hiroo Satoh  Takashi Ishimaru  Yukuya Yamaguchi  Motoaki Kishino 《Journal of Oceanography》2000,56(5):605-605

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Layout design of rockbolts for natural ground reinforcement     

Junji Kato  Keiichiro Ishii  Kenjiro Terada  Takashi Kyoya 《国际地质力学数值与分析法杂志》2014,38(3):236-255

The present study addresses a layout design of rockbolts for reinforcing natural ground structures applying a special optimization method, called multiphase layout optimization. Rockbolts are used to tighten loosed natural ground, and the layout of rockbolts are determined without sufficient information about the physical properties of the ground materials. Because of this uncertainty, unexpected deformation often occurs at the excavation surface of natural ground. In that case, it is requested to determine an effective layout of the additional rockbolts promptly with respect to the actual deformation at the construction site. However, it is not easy to determine the optimal layout because of its complexity, and consequently, it has no choice but to determine the layout in an empirical way. This study introduces a numerical approach to determine an optimal layout of rockbolts with respect to arbitrarily possible deformation of natural ground. The objective is to maximize the stiffness of the overall ground structure reinforced with rockbolts. For optimization, a gradient‐based optimization scheme is applied because of its numerical efficiency. It was verified from a series of numerical examples that this method has great potential to improve the stiffness of the overall ground structure and shows a certain applicability to a practical design. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Erratum: Modelling peculiar velocities of dark matter haloes     

Takashi Hamana  Issha Kayo  Naoki Yoshida  Yasushi Suto  Y. P. Jing 《Monthly notices of the Royal Astronomical Society》2005,357(4):1407-1408

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Magnetic field structures of hard X-ray flares observed by HINOTORI spacecraft     

Takashi Sakurai 《Solar physics》1985,95(2):311-321

The magnetic field structure of five flares observed by HINOTORI spacecraft is studied. The double source structure of impulsive flares seems to indicate hard X-ray emission from the two footpoints of a flaring loop, but the potential field computation does not reproduce a loop connecting the two sources. Therefore the magnetic field could be in a sheared configuration and the force-free field modeling would be the next step to examine. On the other hand gradual flares are characterized by hard X-ray sources located in the corona, 2–4 x 10⁴ km above the photosphere. The potential field modeling is found to give a reasonable fitting in this type of flares, and the hard X-ray sources are located at the top of the magnetic loop or arcade. This configuration is consistent with the thick-target trap model of the hard X-ray bursts.  相似文献   

Possible observational evidence for the θ⁻² angular distribution of the opening half-angle of gamma-ray burst jets     

Daisuke Yonetoku  Ryo Yamazaki  Takashi Nakamura  Toshio Murakami 《Monthly notices of the Royal Astronomical Society》2005,362(3):1114-1118

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Ventilation revealed by the observation of dissolved oxygen concentration south of the Kuroshio Extension during 2012–2013     

Akira?NaganoEmail authorView author&#;s OrcID profile  Toshio?Suga  Yoshimi?Kawai  Masahide?Wakita  Kazuyuki?Uehara  Kyoko?Taniguchi 《Journal of Oceanography》2016,72(6):837-850

From the moored buoy observation at \(33.9^{\circ }\)N, \(144.9^{\circ }\)E south of the Kuroshio Extension (KE), we obtained Eulerian time series of dissolved oxygen concentration (DO) at 200, 400, and 600 m depths from June 2012 to March 2013. We observed ventilation by meso- and submesoscale processes that transport water southward across the KE jet. First, the cyclonic mesoscale eddy in June 2012 substantially depressed DO at depths of 400 and 600 m but maintained DO at 200 m, suggesting near-surface lateral transport of high-DO water derived from the north of the KE. Second, subduction of high-DO (>230 \({\upmu }\)mol kg\(^{-1}\)) water to a depth of 600 m was observed from early February to March 2013, associated with a mesoscale/submesoscale meandering of the KE jet. In mid-March 2013, shipboard hydrographic data were collected where the water mass at the mooring site would be advected by the eastward current on the southern flank of the KE. Based on these data, the subduction event was identified as an intrusion of an anomalously thick water mass from approximately 400–900 dbar. Ventilation of the subtropical mode water at a depth of 200 m around a subsurface DO maximum layer was detected as a rapid rise in DO in January 2013. This occurred after a significant seasonal decrease in DO at a rate of \(-0.130 \pm 0.007\) \({\upmu }\)mol kg\(^{-1}\) day\(^{-1}\) from July to December 2012.  相似文献   

Impact of in-consistency between the climate model and its initial conditions on climate prediction     

Liu  Xueyuan  Köhl  Armin  Stammer  Detlef  Masuda  Shuhei  Ishikawa  Yoichi  Mochizuki  Takashi 《Climate Dynamics》2017,49(3):1061-1075

We investigated the influence of dynamical in-consistency of initial conditions on the predictive skill of decadal climate predictions. The investigation builds on the fully coupled global model “Coupled GCM for Earth Simulator” (CFES). In two separate experiments, the ocean component of the coupled model is full-field initialized with two different initial fields from either the same coupled model CFES or the GECCO2 Ocean Synthesis while the atmosphere is initialized from CFES in both cases. Differences between both experiments show that higher SST forecast skill is obtained when initializing with coupled data assimilation initial conditions (CIH) instead of those from GECCO2 (GIH), with the most significant difference in skill obtained over the tropical Pacific at lead year one. High predictive skill of SST over the tropical Pacific seen in CIH reflects the good reproduction of El Niño events at lead year one. In contrast, GIH produces additional erroneous El Niño events. The tropical Pacific skill differences between both runs can be rationalized in terms of the zonal momentum balance between the wind stress and pressure gradient force, which characterizes the upper equatorial Pacific. In GIH, the differences between the oceanic and atmospheric state at initial time leads to imbalance between the zonal wind stress and pressure gradient force over the equatorial Pacific, which leads to the additional pseudo El Niño events and explains reduced predictive skill. The balance can be reestablished if anomaly initialization strategy is applied with GECCO2 initial conditions and improved predictive skill in the tropical Pacific is observed at lead year one. However, initializing the coupled model with self-consistent initial conditions leads to the highest skill of climate prediction in the tropical Pacific by preserving the momentum balance between zonal wind stress and pressure gradient force along the equatorial Pacific.

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Calculation of force-free magnetic field with non-constant α     

Takashi Sakurai 《Solar physics》1981,69(2):343-359

A numerical method is developed for solving the force-free magnetic field equation, × B = B, with spatially-varying . The boundary conditions required are the distribution of B _n (viz. normal component of the field on the photosphere) as well as the value of in the region of positive (or negative) B _n . Examples of calculations are presented for a simple model of a solar bipolar magnetic region. It is found that the field configuration and the energy stored in the field depend crucially on the distribution of . The present method can be applied to a more complex configuration observed on the Sun by making use of actual magnetic field measurements.On leave of absence from Department of Astronomy, University of Tokyo.  相似文献   

Some hydrodynamic problems for a nepheloid zone     

Takashi Ichiye 《Pure and Applied Geophysics》1966,63(1):179-195

Summary A layer of a few hundred meters thickness with suspended matter (a nepheloid zone) was discovered byEwing andThorndike [4]³⁾ near the bottom on the continental slope of the North Atlantic. A downward pressure gradient is produced in this layer due to increment of water density with suspensoid. When only the Coriolis force balances with this pressure gradient, a bottom nepheloid current flows southwestward parallel to the depth contours with a velocity of about 10 (cm/sec) for a slope of one degree. The pressure gradient for fluid with locally variable density above a sloping bottom is treated and an extra term due to density gradient along the slope is derived. The vertical profiles of the nepheloid current with an effect on the vertical eddy viscosity are computed. Two kinds of vertical distributions of eddy viscosity are determined from the observed nepheloid distributions and used in the calculations: constant but different values at two layers and those increasing with height. The effect of the change of density along the bottom is treated by introducing dimensionless variables. Rossby number of the nepheloid current becomes about 10^–2 indicating inertia terms to be negligible. Rossby number of turbidity currents ranges from 2 (in a decaying area) to 5 (developing area), suggesting that inertia terms are more important than Coriolis terms. The trajectories of turbidity currents are computed from motion of a mass of mud under the Coriolis force and friction, and the results are applied to those inferred byHand andEmery [6] in the San Diego Through off California.LGO Contribution Number 925.  相似文献   

Diel Changes in Vertical Distribution and Feeding Conditions of the Chaetognath Parasagitta elegans (Verill) in the Subarctic Pacific in Summer     

Sohey Matsuda  Akira Taniguchi 《Journal of Oceanography》2001,57(3):353-360

Diel changes in vertical distribution and feeding conditions of the chaetognath Parasagitta elegans (Verill) were observed in three regions of the subarctic North Pacific in the summer of 1997. Samples were collected by repeated vertical hauls with a Vertical Multiple Plankton Sampler (VMPS) for 15–45 hours by demarcating the 0–500 m water column into four sampling layers. Integrated abundance through the entire water column and the proportion of juveniles were higher in the Bering Sea than the western and eastern subarctic Pacific. Juveniles always inhabited the surface layer in the western subarctic Pacific and Bering Sea, but they inhabited the underlying layer in the eastern subarctic Pacific. Stages I–III concentrated into the upper 150 m in the western subarctic Pacific but were distributed widely from 20–300 m in the Bering Sea. Among them, Stages II and III migrated rather synchronously over a wide vertical range in the eastern subarctic Pacific. The feeding rate of P. elegans was calculated to be 0.18 prey/chaetognath/day in the western subarctic Pacific, 0.27 prey/chaetognath/day in the Bering Sea and 0.07 prey/chaetognath/day in the eastern subarctic Pacific.  相似文献