A direct numerical approach to the Chandrasekhar'sH-functions for arbitrary characteristic functions     

Kiyoshi Kawabata  Takehiko Satoh  Sueo Ueno 《Astrophysics and Space Science》1991,182(2):249-260

The purpose of this paper is to present a numerical technique to directly compute the Chandrasekhar'sH ()-function for anisotropic scattering in terms of the roots of the characteristic equations as well as the quadrature points of a certain degreen employed to approximate the definite integral involved in the basic equation. The principal feature of the algorithm proposed here is a compact computer code to enumerate _n C _m combinations ofn distinct integers {1,...,n} takenm at a time. With these quantities available, the coefficients of the polynomial equation of the characteristics equation can be readily computed for any given characteristic function, so that a standard technique such as the Laguerre method can be applied to find all the roots.It is shown that the results obtained for some representativeH()-functions using the present technique with relatively low-order formula (e.g.,n=7) are sufficiently accurate for all practical purposes.  相似文献   

Some regular patterns in the distribution of sediment contamination in the coastal waters along Japan     

Yasushi Hiraizumi  Takehiko Manabe  Hajime Nishimura 《Journal of Oceanography》1978,34(5):222-232

Observations of sediment contamination along the coast of Japan were analyzed. When the pollutant concentration is divided by the fine particle fraction in the sediment, a regular pattern is observed in the quantitative relationship among the degree and the area of contamination and the discharge rate of pollutant released continuously into the water along the coast. This regularity was observed with respect to COD,n-hexane soluble substances and heavy metals, and could be expressed by a formula.Polluted particles were supposed to disperse through suspension in the bottom water layer, and thus their distribution in the surface sediment is expected to become similar to effluent dispersion in the surface water.  相似文献   

Structure of the strong tidal jet in the naruto strait     

Yoshio Takasugi  Tateki Fujiwara  Takehiko Higo 《Journal of Oceanography》1990,46(3):69-83

In order to clarify the structure of the strong tidal current at the Naruto Strait in the Seto Inland Sea of Japan, the sea-level values were observed in the strait and the current measurements were made with an Acoustic Doppler Current Profiler (ADCP).The tidal volume transports for M₂ and S₂ tides were about 74×10³ and 26×10³ m³ sec^–1, respectively. The horizontal profile of the velocity at the phase of the strong tidal current compares favorably with a theoretical profile of the two-dimensional steady turbulent jet except for the side parts of the profile. Moreover, the entrainment rate of the surrounding water into the strong tidal jet was estimated from the difference of mass flux between two cross-sections at the strait, the entrainment rate and entrainment constant for both the northward and southward flows being about 1.3–2.5×10^–4m^–1 and about 0.03–0.05, respectively.  相似文献   

Lattice preferred orientation in CaIrO<Subscript>3</Subscript> perovskite and post-perovskite formed by plastic deformation under pressure     

Ken Niwa  Takehiko Yagi  Kenya Ohgushi  Sébastien Merkel  Nobuyoshi Miyajima  Takumi Kikegawa 《Physics and Chemistry of Minerals》2007,34(9):679-686

Lattice preferred orientations (LPO) developed in perovskite and post-perovskite structured CaIrO₃ were studied using the radial X-ray diffraction technique combined with a diamond anvil cell. Starting materials of each phase were deformed from 0.1 MPa to 6 GPa at room temperature. Only weak LPO was formed in the perovskite phase, whereas strong LPO was formed in the post-perovskite phase with an alignment of the (010) plane perpendicular to the compression axis. The present result suggests that the (010) is a dominant slip plane in the post-perovskite phase and it is in good agreement with the crystallographic prediction, dislocation observations via transmission electron microscopy, and a recent result of simple shear deformation experiment at 1 GPa–1,173 K. However, the present result contrasts markedly from the results on MgGeO₃ and (Mg,Fe)SiO₃, which suggested that the (100) or (110) is a dominant slip plane with respect to the post-perovskite structure. Therefore it is difficult to discuss the behavior of the post-perovskite phase in the Earth’s deep interior based on existing data of MgGeO₃, (Mg,Fe)SiO₃ and CaIrO₃. The possible sources of the differences between MgGeO₃, (Mg,Fe)SiO₃ and CaIrO₃ are discussed.  相似文献   

Effect of incorporation of iron and aluminum on the thermoelastic properties of magnesium silicate perovskite     

Norimasa Nishiyama  Takehiko Yagi  Shigeaki Ono  Hirotada Gotou  Tatsuhiko Harada  Takumi Kikegawa 《Physics and Chemistry of Minerals》2007,34(3):131-143

In situ X-ray diffraction measurements of Fe- and Al-bearing MgSiO₃-rich perovskite (FeAl-Pv), which was synthesized from a natural orthopyroxene, were performed at pressures of 19–32 GPa and temperatures of 300–1,500 K using a combination of a Kawai-type apparatus with eight sintered-diamond anvils and synchrotron radiation. Two runs were performed using a high-pressure cell with two sample chambers, and both MgSiO₃ perovskite (Mg-Pv) and FeAl-Pv were synthesized simultaneously in the same cell. Thus we were able to measure specific volumes (V/V ₀) of Mg-Pv and FeAl-Pv at the same P−T conditions. At all the measurement conditions, values of the specific volume of FeAl-Pv are consistent with those of Mg-Pv within 2 Standard Deviation, strongly suggesting that effect of incorporation of iron and aluminum on the thermoelastic properties of magnesium silicate perovskite is undetectable in this composition, pressure, and temperature range. Two additional runs were performed using a high-pressure cell that has one sample chamber and unit-cell volumes of FeAl-Pv were measured at pressures and temperatures up to 32 GPa and 1,500 K, respectively. All the unit-cell volume data of FeAl-Pv perovskite were fitted to the high temperature Birch–Murnaghan equation of state and a complete set of thermoelastic parameters of this perovskite was determined with an assumption of K′ _300,0 = 4. The determined parameters are K _300,0 = 243(3) GPa, (∂K _T,0/∂T) _P = −0.030(8) GPa/K, a ₀ = 2.78(18) × 10⁻⁵ K⁻¹, and b ₀ = 0.88(28) × 10⁻⁸ K⁻², where a ₀ and b ₀ are the coefficients of the following expression describing the zero-pressure thermal expansion: α _T,0 = a ₀ + b ₀ T. The equation-of-state parameters of FeAl-Pv are in good agreement with those of MgSiO₃ perovskite at the conditions corresponding to the uppermost part of the lower mantle.  相似文献   

Vertical material flux under seasonal sea ice in the Okhotsk Sea north of Hokkaido, Japan     

Takehiko Hiwatari  Kunio Shirasawa  Yasushi Fukamachi  Ryuichi Nagata  Tomoyoshi Koizumi  Hiroshi Koshikawa  Kunio Kohata 《Polar Science》2008,2(1):41-54

Downward material fluxes under seasonal sea ice were measured using a time-series sediment trap installed at an offshore site in the Okhotsk Sea north of Hokkaido, Japan, from 13 January to 23 March 2005. The maximum fluxes of lithogenic material (753 mg m⁻² day⁻¹) and organic matter (mainly detritus; 333 mg m⁻² day⁻¹) were recorded during the period in which sea ice drifted ashore and increased in extent, from 13 January to 9 February. Organic matter as fecal pellets (81–93 mg m⁻² day⁻¹) and opal as biosilica (51–67 mg m⁻² day⁻¹), representing diatom fluxes, were abundant in sediment trap samples obtained during the period of full sea ice coverage from 10 February to 9 March. Microscopic observations revealed that fecal pellets were largely diatom frustules, suggesting that zooplankton actively grazed on ice algae during the period of full sea ice coverage. During the period of retreating sea ice, from 10 to 23 March, the phytoplankton flux showed a rapid increase (from 9.5 to 22.5 × 10⁶ cells m⁻² day⁻¹), reflecting their release into the water column as the sea ice melted. Our results demonstrate that the quantity and quality of sinking biogenic and lithogenic materials vary with the seasonal extent of sea ice in mid-winter.  相似文献   

A basic study on the application of LRFD in “the technical standard for port and harbour facilities in Japan”: a case of gravity type quay wall in a persistent design situation     

Masahiro Takenobu  Masafumi Miyata  Yu Otake  Takehiko Sato 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2019,13(3):195-204

ABSTRACT

The Partial Factor Method (PFM) based on the Level 1 reliability design method was introduced in 2007 to the Technical Standards for Port and Harbour Facilities (TSPHF-2007) in Japan. After nearly 10 years of practical use of TSPHF-2007, the design standard has been revised based on requests from the practitioners who recommend the transition from the PFM to the Load Resistance Factor Design (LRFD). In this paper, we discuss the setting method of the target failure probability to determine the partial factors based on code calibration. Furthermore, we examine the impacts of implementing the LRFD concept to the TSPHF by taking the sliding and overturning of a gravity type quay wall as an example to represent port and harbour facilities. We found no practical difference in caisson width derived using the LRFD and the PFM, whereas the degree of matching of the target failure probability was somewhat more precise for the PFM. This finding indicates that the LRFD is a more reasonable design method than the PFM in terms of the simplicity of the performance function itself and the ease of engineering interpretation during the design procedure.  相似文献   

Predictability of storm wave heights in the ice-free Beaufort Sea     

Takehiko Nose  Adrean Webb  Takuji Waseda  Jun Inoue  Kazutoshi Sato 《Ocean Dynamics》2018,68(10):1383-1402

A predictability study on wave forecast of the Arctic Ocean is necessary to help identify hazardous areas and ensure sustainable shipping along the trans-Arctic routes. To assist with validation of the Arctic Ocean wave model, two drifting wave buoys were deployed off Point Barrow, Alaska for two months in September 2016. Both buoys measured significant wave heights exceeding 4 m during two different storm events on 19 September and 22 October. The NOAA-WAVEWATCH III^? model with 16-km resolution was forced using wind and sea ice reanalysis data and obtained general agreement with the observation. The September storm was reproduced well; however, model accuracy deteriorated in October with a negative wave height bias of around 1 m during the October storm. Utilising reanalysis data, including the most up-to-date ERA5, this study investigated the cause: grid resolution, wind and ice forcing, and in situ sea level pressure observations assimilated for reanalysis. The analysis has found that there is a 20% reduction of in situ SLP observations in the area of interest, presumably due to fewer ships and deployment options during the sea ice advance period. The 63-member atmospheric ensemble reanalysis, ALERA2, has shown that this led to a larger ensemble spread in the October monthly mean wind field compared to September. Since atmospheric physics is complex during sea ice advance, it is speculated that the elevated uncertainty of synoptic-scale wind caused the negative wave model bias. This has implications for wave hindcasts and forecasts in the Arctic Ocean.  相似文献   

霞浦湖沉积物需氧速率的研究   总被引：5，自引：1，他引：5  

范成新  相崎守弘  福岛武彦  松重一夫 《海洋与湖沼》1998,29(5):508-513

１９９５年２月,用大口径采样器采集日本霞浦湖土浦湾和湖心柱状沉积物样品,在２０℃恒温蔽光封闭条件下,研究了该湖泊沉积物需氧（ＳＯＤ）速率及实验前后上覆水和间隙水中形态营养物浓度变化,结果表明,实验初期（０－５ｈ）ＳＯＤ速率随时间呈线性上升,大于５ｈ后呈非线性下降,对线性部分计算的ＳＯＤ速率约在０．６－１．８ｍｇ／（ｍ＾２．ｄ）之间,实验发现,上覆水和表层间隙水中形态营养物Ｆｅ（Ⅱ）,ＮＨ＾＋４－Ｎ  相似文献   

Anomalous behavior of cristobalite in helium under high pressure     

Tomoko Sato  Hiroto Takada  Takehiko Yagi  Hirotada Gotou  Taku Okada  Daisuke Wakabayashi  Nobumasa Funamori 《Physics and Chemistry of Minerals》2013,40(1):3-10

We have investigated the high-pressure behavior of cristobalite in helium by powder X-ray diffraction. Cristobalite transformed to a new phase at about 8 GPa. This phase is supposed to have a molar volume of about 30 % larger than cristobalite, suggesting the dissolution of helium atoms in its interstitial voids. On further compression, the new phase transformed to a different phase which showed an X-ray diffraction pattern similar to cristobalite X-I at about 21 GPa. On the other hand, when the new phase was decompressed, it transformed to another new phase at about 7 GPa, which is also supposed to have a molar volume of about 25 % larger than cristobalite. On further decompression, the second new phase transformed to cristobalite II at about 2 GPa. In contrast to cristobalite, quartz did not show anomalous behavior in helium. The behavior of cristobalite in helium was also consistent with that in other mediums up to about 8 GPa, where the volume of cristobalite became close to that of quartz. These results suggest that dissolution of helium may be controlled not only by the density (amount of voids) but also by the network structure of SiO₄ tetrahedra (topology of voids).  相似文献