The theory of the nutation for the rigid earth model at the second order   总被引：6，自引：0，他引：6  

Hiroshi Kinoshita  Jean Souchay 《Celestial Mechanics and Dynamical Astronomy》1990,48(3):187-265

We perform a complete reconstruction of the series of the nutation for a rigid Earth model with the use of the very accurate theories ELP2000 and VSOP82 for the motion of the Moon and the planets respectively, in such a way that all the individual contributions up to 0.005 mas should be taken. This implies the introduction of the planetary effects, of the influence of second-order parts of the potential of the Earth (J3, triaxiality), and some improvements due to an extension of the theory at the second order. All this increase notably the number of coefficients to be taken in account, and modifies also in a significant way the value of some of them.  相似文献   

Under‐ice salinity and stable isotope distribution of Saroma‐ko Lagoon,Hokkaido, northern Japan     

Maki Morimoto  Kyoko Kawanobe  Osamu Abe  Takayoshi Kawai  Toshiyuki Kawamura  Kunio Shirasawa 《水文研究》2010,24(7):904-916

In winter, lakes and lagoons at high altitudes or high latitudes have interesting hydrological cycles that differ from those in other seasons or in other regions, because water surfaces are covered with ice. Hydrological balances of lakes and lagoons are complex dynamic systems, and to elucidate them, isotopic tracers of water have been used as effective tools along with observations of precipitation, evaporation, inflows, and outflows. Here, to understand hydrological processes during freezing periods in the brackish Saroma‐ko Lagoon, Hokkaido, northern Japan, we examined horizontal and vertical distributions of salinity and isotope compositions of lagoon water and ice in 2005 and 2006. Horizontal and vertical gradients of salinity and isotope compositions were observed from the river mouth to the sea channel, and factors determining these distributions were considered. The mixing of freshwater and seawater and a freezing effect were presumed to be factors in relationships between salinity and isotopes and in relationships between surface waters and ice just above the water. A simple box model for water balance was constructed based on these putative factors to reproduce the distributions of salinity and isotope compositions of surface waters and ice. An evaluation of the model revealed that this hydrological system is controlled primarily by horizontal advection of the epilimnion, freshwater influx, and the ice growth rate. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

From an initial transient-state to a steady-state in metamorphic reactions: An experimental approach in the system dolomite-quartz-H₂O     

Tadao  Nishiyama  Aiko  Tominaga  Hiroshi  Isobe 《Island Arc》2007,16(1):16-27

Abstract We carried out hydrothermal experiments in the system dolomite‐quartz‐H₂O to track the temporal change in reaction rates of simultaneous reactions during the development of reaction zones. Two types of configurations for the starting materials were prepared: dolomite single crystals + quartz powder + water and quartz single crystals + dolomite powder + water, both sealed separately in gold capsules. Runs at 0.1GPa and 600°C with cold seal pressure vessels gave the following results. (i) In short duration (45–71 h) runs metastable layer sequences involving wollastonite and talc occur in the reaction zone, whereas they disappear in longer duration (168–336 h) runs. (ii) The layer sequence of the reaction zones in short duration runs differs from place to place on the dolomite crystal even in the same run. (iii) The diversity of layer sequences in the short duration runs merges into a unique layer sequence in the longer duration runs. (iv) The reaction zone develops locally on the dolomite crystal, but no reaction zone was observed on the quartz crystal in any of the runs. The lines of evidence (i)–(iii) show that the system evolves from an initial transient‐ to a steady‐state and that the kinetic effect is important in the development of reaction zones. A steady diffusion model for the unique layer sequence Qtz/Di/Fo + Cal/Dol + Cal/Dol shows that the Dol + Cal layer cannot be formed by diffusion‐controlled process and that the stability of the layer sequence Qtz/Di/Fo + Cal/Dol depends not only on L‐ratios (a = /L_CaOCaO and b = /L_MgOMgO) but also on the relative rate P = (−2ξ₁ − ξ₂)/(–ξ₁ − 2ξ₂) of competing reactions: Dol + 2Qtz = Di + 2CO₂ (ξ₁) and 2Dol + Qtz = Fo + 2Cal + 2CO₂ (ξ₂). For smaller P the stability field will shift to higher values of a and b. The steady diffusion model also shows that the apparent‐non‐reactivity on the quartz surface can be attributed to void formation in a large volume fraction in the diopside layer.  相似文献   

High-resolution observations of dissolved isoprene in surface seawater in the Southern Ocean during austral summer 2010–2011     

Sohiko Kameyama  Satoshi Yoshida  Hiroshi Tanimoto  Satoshi Inomata  Koji Suzuki  Hisayuki Yoshikawa-Inoue 《Journal of Oceanography》2014,70(3):225-239

We measured dissolved isoprene (2-methyl-1,3-butadiene; C₅H₈) concentrations in a broad area of the southern Indian Ocean and in the Indian sector of the Southern Ocean from 35°S to 64°S and from 37°E to 111°E during austral summer 2010–2011. Isoprene concentrations were continuously measured by use of a proton-transfer-reaction mass spectrometer combined with a bubbling-type equilibrator. Concentrations of isoprene and its emission flux throughout the study period ranged from 0.2 to 395 pmol L^?1 and from 181 to 313 nmol m^?2 day^?1, respectively, the averages being generally higher than those of previous studies. Although we found a significant linear positive relationship between isoprene and chlorophyll-a concentrations (r ² = 0.37, n = 36, P < 0.001), the correlation coefficient was lower than previously reported. In contrast, in the high-latitude area (>53°S) we identified a significant negative correlation (r ² = 0.59, n = 1263, P < 0.001) between isoprene and the temperature-normalized partial pressure of carbon dioxide (n-pCO₂), used as an indicator of net community production in this study. This suggests that residence times and factors controlling variations in isoprene and n-pCO₂ are similar within a physically stable water column.  相似文献   

Large-Eddy Simulation of Pollutant Removal from a Three-Dimensional Street Canyon   总被引：3，自引：3，他引：0  

Takenobu Michioka  Hiroshi Takimoto  Ayumu Sato 《Boundary-Layer Meteorology》2014,150(2):259-275

Large-eddy simulations were conducted to investigate the mechanism of pollutant removal from a three-dimensional street canyon. Five block configurations with aspect ratios (building height to length) of 1, 2, 4, 8 and $\infty $ were used to create an urban-like array. A pollutant was released from a ground-level line source at the centre of the target canyon floor. For smaller aspect ratios, the relative contribution of the turbulent mass flux to net mass flux at the roof level, which was spatially averaged along the roof-level ventilation area, was closer to unity, indicating that turbulent motions mainly affected pollutant removal from the top of the canyon. As aspect ratio increased, the relative contribution became smaller, owing to strong upwind motions. However, the relative contribution again reached near unity for the infinite aspect ratio (i.e. a two-dimensional street canyon) because of lowered lateral flow convergence. At least 75 % of total emissions from the three-dimensional street canyon were attributable to turbulent motions. Pollutant removal by turbulent motions was related to the coherent structures of low-momentum fluid above the canyons. Though the coherent structure size of the low-momentum fluid differed, the positions of low-momentum fluid largely corresponded to instantaneous high concentrations of pollutant above the target canyon, irrespective of canyon geometry.  相似文献   

Solid‐state 13C NMR characterization of insoluble organic matter from Antarctic CM2 chondrites: Evaluation of the meteoritic alteration level     

Hikaru YABUTA  Hiroshi NARAOKA  Kinya SAKANISHI  Hiroyuki KAWASHIMA 《Meteoritics & planetary science》2005,40(5):779-787

Abstract— Chemical structures of the insoluble organic matter (IOM) from the Antarctic CM2 chondrites (Yamato [Y‐] 791198, 793321; Belgica [B‐] 7904; Asuka [A‐] 881280, 881334) and the Murchison meteorite were analyzed by solid‐state ¹³C nuclear magnetic resonance (NMR) spectroscopy. Different types of carbons were characterized, such as aliphatic carbon (Ali‐C), aliphatic carbon linked to hetero atom (Hetero‐Ali‐C), aromatic carbon (Aro‐C), carboxyls (COOR), and carbonyls (C=O). The spectra of the IOM from Murchison and Y‐791198 showed two major peaks: Ali‐C and Aro‐C, while the spectra from the other meteorites showed only one major peak of Aro‐C. Carbon distribution was determined both by manual integration and deconvolution. For most IOM, the Aro‐C was the most abundant (49.8–67.8%) of all carbon types. When the ratios of Ali‐C to Aro‐C (Ali/Aro) were plotted with the atomic hydrogen to carbon ratio (H/C), a correlation was observed. If we use the H/C as a parameter for the thermal alteration event on the meteorite parent body, this result shows a different extent of thermal alteration. In addition, IOM with a lower Ali/Aro showed a lower ratio of Ali‐C to COOR plus C=O (Ali / (COOR + C=O)). This result suggests that the ratio of CO moieties to aliphatic carbon in IOM might reflect chemical oxidation that was involved in hydrothermal alteration.  相似文献   

Textural variations and impact history of the Millbillillie eucrite     

Akira Yamaguchi  Hiroshi Takeda  Donald D. Bogard  Daniel Garrison 《Meteoritics & planetary science》1994,29(2):237-245

Abstract— We have investigated 10 new specimens of the Millbillillie eucrite to study its textures and mineral compositions by electron probe microanalyser and scanning electron microscope. Although originally described as having fine-grained texture, the new specimens show diversity of texture. The compositions (Mg/Fe ratios) of the host pigeonites and augite lamellae are homogeneous, respectively, in spite of the textural variation. In addition to their chemical homogeneity, pyroxenes in coarse and fine-grained clasts are partly inverted to orthopyroxene. Chemical zoning of plagioclase during crystal growth is preserved. This eucrite includes areas of granulitic breccias and impact melts. Large scale textures show a subparallel layering suggesting incomplete mixing and deposition of impact melt and lithic fragments. An ³⁹Ar-⁴⁰Ar age determination for a coarse-grained clast indicates a strong degassing event at 3.55 ± 0.02 Ga. We conclude that Millbillillie is among the most equilibrated eucrites produced by thermal annealing after impact brecciation. According to the classification of impact breccias, Millbillillie can be classified as a mixture of granulitic breccias and impact melts. The last significant thermal event is characterized by network-like glassy veins that run through clasts and matrices. Consideration of textural observations and requirements for Ar-degassing suggests that the ³⁹Ar-⁴⁰Ar age could in principle date either the earilier brecciation and annealing event or the event which produced the veins.  相似文献   

Key natural analogue input required to build a safety case for direct disposal of spent nuclear fuel in Japan     

Ian G. McKinley  Hideki Kawamura  Susie M. L. Hardie  Elizaveta Klein  Tara M. Beattie 《Swiss Journal of Geoscience》2015,108(1):147-154

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Physical properties and isotopic characteristics of landfast sea ice around the North Water (NOW) Polynya region     

Toshiyuki Kawamura  Kunio Shirasawa  Kunio Kobinata 《大气与海洋》2013,51(3):173-182

Abstract

An ice core sampling program was conducted during the North Water (NOW) Polynya Project 1998 Experiment in northern Baffin Bay during April‐May 1998. The physical properties of snow and sea ice as well as the microstructure and stable isotopic composition of first‐year landfast sea ice near the polynya were investigated. The thickness of sea ice at the sampling sites ranged between 147 and 194 cm with thinner snow cover during the period between mid‐April and late May. The ice was characterized as typical first‐year landfast sea ice, being composed of a thin granular ice layer at the top and an underlying columnar ice layer towards the bottom of the ice. The samples obtained at a site closer to the ice edge of the polynya contained a thin granular ice layer originating from frazil ice near the ice bottom. Formation of frazil ice was considered to be caused by turbulent processes induced by winds, waves and currents forced from the polynya and also mixing with water masses produced at the polynya.  相似文献   

A study of Mg and K isotopes in Allende CAIs: Implications to the time scale for the multiple heating processes     

Motoo Ito  Hiroshi Nagasawa  Hisayoshi Yurimoto 《Meteoritics & planetary science》2006,41(12):1871-1881

Abstract— The measurements of magnesium and potassium isotopic compositions of refractory minerals in Allende calcium‐aluminum‐rich inclusions (CAIs), 7R‐19–1, HN3–1, and EGG3 were taken by secondary ion mass spectrometry (SIMS). The 7R‐19–1 contains ¹⁶O‐rich and ¹⁶O‐poor melilite grains and define a single isochron corresponding to an initial ²⁶Al/²⁷Al ratio of (6.6 ± 1.3) × 10^?5. The Al‐Mg isochron, O isotope measurements and petrography of melilite in 7R‐19–1 indicate that ¹⁶O‐poor melilite crystallized within 0.4 Myr after crystallization of ¹⁶O‐rich melilite, suggesting that oxygen isotopic composition of the CAI‐forming region changed from ¹⁶O‐rich to ¹⁶O‐poor within this time interval. The ¹⁶O‐poor melilite is highly depleted in K compared to the adjacent ¹⁶O‐rich melilite, indicating evaporation during remelting of 7R‐19–1. We determined the isochron for ⁴¹Ca‐⁴¹K isotopic systematics in EGG3 pyroxene with (4.1 ± 2.0) × 10^?9 (2s?) as an initial ratio of ⁴¹Ca/⁴⁰Ca, which is at least two times smaller than the previous result (Sahijipal et al. 2000). The ratio of ⁴¹Ca/⁴⁰Ca in the EGG3 pyroxene grain agrees within error with the value obtained by Hutcheon et al. (1984). No evidence for the presence of ⁴¹K excess (decay product of a short‐lived radionuclide ⁴¹Ca) was found in 7R‐19–1 and HN3–1. We infer that the CAI had at least an order of magnitude lower than canonical ⁴¹Ca/⁴⁰Ca ratio at the time of the CAI formation.  相似文献