57Fe mössbauer study of synthetic Fe3+-melilites     

Masahide Akasaka  Haruo Ohashi 《Physics and Chemistry of Minerals》1985,12(1):13-18

Synthetic Fe³⁺-melilites containing NaCaFe³⁺-Si₂O₇-, Ca₂Fe³⁺AlSiO₇- or Sr₂Fe³⁺AlSiO₇-components have been studied by ⁵⁷Fe Mössbauer spectroscopy. The spectrum of åkermanite containing an NaCaFe³⁺Si₂O₇-component consists of one doublet identified to belong to Fe³⁺ in T1 sites. The spectra of åkermanite and gehlenite containing Ca₂Fe³⁺ AlSiO₇- or Sr₂Fe³⁺ AlSiO₇-component consist of two doublets. The inner and outer doublets are identified to belong to Fe³⁺ in the less distorted T1 and that in the more distorted T2 sites, respectively. The area ratios of the spectra show that the site occupancy of Fe³⁺ (T1) in gehlenite is less than that in åkermanite in which the distribution of Fe³⁺ in T1 and T2 sites is apparently random. The different distributions can be explained in terms of competition between minimizing the deficiency in the electrostatic valence and the preference of Al for T1 sites which the isomer shift measurements show to be more ionic.  相似文献   

A preliminary study of D/H ratios of chlorites     

Yoshimasu Kuroda  Tetsuro Suzuoki  Sadao Matsuo  Haruo Shirozu 《Contributions to Mineralogy and Petrology》1976,57(2):223-225

Chemistry dependence of D of chlorites is inferred from data for natural chlorites. D of water equilibrated with those chlorites is estimated to be –2–8.  相似文献   

Non-linear models for simulating the dynamic damaging process of low-rise reinforced concrete buildings during severe earthquakes     

Haruo Takizawa 《地震工程与结构动力学》1975,4(1):73-94

This paper is a study of idealizing a planar reinforced concrete frame as a non-linear dynamic system for the purpose of simulating its inelastic behaviour during severe earthquakes. After having estimated the restoring force characteristics of all constituent members by experimental means (represented, for example, by a group of empirical equations), it is possible to estimate the non-linear characteristics of the complete structure and to trace the damaging process for each constituent member under a given ground motion disturbance. However, this technique, which is directly based on member-level properties, generally requires rather laborious computational procedures; for practical reasons it is necessary to develop a simplified model, reducing the required calculation without losing the substance of the mechanical phenomena. Thus the reliability of simplification by conventional shear modelling is examined in direct comparison with the response results from rigorous modelling. It is concluded that the shear modelling generally yields an inadequate and, in many cases, erroneous result. The primary cause leading to this discrepancy is identified and, based on this discussion, a more appropriate modelling as simple as conventional shear modelling is proposed.  相似文献   

The high-pressure C2/c–P21/c phase transition along the LiAlSi2O6–LiGaSi2O6 solid solution     

Fabrizio Nestola  Tiziana Boffa Ballaran  Haruo Ohashi 《Physics and Chemistry of Minerals》2008,35(8):477-484

Two synthetic single-crystals with composition Li(Al_0.53Ga_0.47)Si₂O₆ and LiGaSi₂O₆ and space group C2/c at room conditions have been studied under pressure by means of X-ray diffraction using a diamond anvil cell. The unit-cell parameters were determined at 12 and 10 different pressures up to P = 8.849 and P = 7.320 GPa for Li(Al_0.53Ga_0.47)Si₂O₆ and LiGaSi₂O₆, respectively. The sample with mixed composition shows a C2/c to P2₁/c phase transformation between 1.814 and 2.156 GPa, first-order in character. The transition is characterised by a large and discontinuous decrease in the unit-cell volume and by the appearance of the b-type reflections (h + k = odd) typical of the primitive symmetry. The Ga end-member shows the same C2/c to P2₁/c transformation at a pressure between 0.0001 and 0.39 GPa. The low-pressure value at which the transition occurred did not allow collecting any data in the C2/c pressure stability field except that on room pressure. Our results compared with those relative to spodumene (LiAlSi₂O₆, Arlt and Angel 2000a) indicate that the substitution of Al for Ga at the M1 site of Li-clinopyroxenes strongly affects the transition pressure causing a decrease from 3.17 GPa (spodumene) to less than 0.39 GPa (LiGaSi₂O₆) and decreases the volume discontinuity at the transition. As already found for other compounds, the C2/c low-pressure phases are more rigid than the P2₁ /c high-pressure ones. Moreover, the increase of the M1 cation radius causes a decrease in the bulk modulus K _T0. The axial compressibility among the Li-bearing clinopyroxenes indicates that the c axis is the most rigid for the C2/c phases while it becomes the most compressible for the P2₁ /c phases.  相似文献   

Optical spectroscopic study of synthetic NaScSi<Subscript>2</Subscript>O<Subscript>6</Subscript>–CaNiSi<Subscript>2</Subscript>O<Subscript>6</Subscript> pyroxenes at normal and high pressures     

Michail N. Taran  Haruo Ohashi  Monika Koch-Müller 《Physics and Chemistry of Minerals》2008,35(3):117-127

Six synthetic NaScSi₂O₆–CaNiSi₂O₆ pyroxenes were studied by optical absorption spectroscopy. Five of them of intermediate (Na_1−x , Ca _x )(Sc_1−x , Ni _x )Si₂O₆ compositions show spectra typical of Ni²⁺ in octahedral coordination, more precise Ni²⁺ at the M1 site of the pyroxene structure. The common feature of all spectra is three broad absorption bands with maxima around 8,000, 13,000 and 24,000 cm⁻¹ assigned to ³ A _2g → ³ T _2g, ³ A _2g → ³ T _1g and →³ T _1g (³ P) electronic spin-allowed transitions of ^VINi²⁺. A weak narrow peak at ∼14,400 cm⁻¹ is assigned to the spin-forbidden ³ A _2g → ¹ T _2g (¹ D) transition of Ni²⁺. Under pressure the spin-allowed bands shift to higher energies and change in intensity. The octahedral compression modulus, calculated from the shift of the ³ A _2g → ³ T _2g band in the (Na_0.7Ca_0.3)(Sc_0.7Ni_0.3)Si₂O₆ pyroxene is evaluated as 85±20 GPa. The Racah parameter B of Ni²⁺(M1) is found gradually changing from ∼919 cm⁻¹ at ambient pressure to ∼890 cm⁻¹ at 6.18 GPa. The Ni end-member pyroxene [(Ca_0.93 Ni_0.07)NiSi₂O₆] has a spectrum different from all others. In addition to the above mentioned bands of Ni²⁺(M1) it displays several new relatively intense and broad extra bands, which were attributed to electronic transitions of Ni²⁺ at the M2 site. In difference to CaO₈ polyhedron geometry of an eightfold coordination, Ni²⁺(M2)O₈ polyhedra are assumed to be relatively large distorted octahedra. Due to different distortions and different compressibilities of the M1 and M2 sites the Ni²⁺(M1)- and Ni²⁺(M2)-bands display rather different pressure-induced behaviors, becoming more resolved in the high-pressure spectra than in that measured at atmospheric pressure. The octahedral compression modulus of Ni²⁺(M1) in this end-member pyroxene is evaluated as 150 ± 25 GPa, which is noticeably larger than in Ni_0.3 pyroxene. This is due to a smaller size and, thus, a stiffer character of Ni²⁺(M1)O₆ octahedron in the (Ca_0.93Ni_0.07)NiSi₂O₆ pyroxene compared to (Na_0.7Ca_0.3)(Sc_0.7Ni_0.3)Si₂O₆.

Monika Koch-MüllerEmail:

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Reconstruction of paleotemperatures in the Northwest Pacific over the past 3000 years from δO values of the micro-bivalvia Carditella iejimensis found in a submarine cave     

Nagisa Yamamoto  Akihisa Kitamura  Tomohisa Irino  Tomoki Kase  Syu-ichi Ohashi 《Global and Planetary Change》2008,62(1-2):97-106

We measured the δ¹⁸O values of the whole shells of the cavernicolous micro-bivalvia Carditella iejimensis obtained from sediments within a submarine cave (31 m water depth) at Ie Island (Okinawa Island, Japan) in the subtropical Northwest Pacific. Our results show no significant millennial-scale trend in the δ¹⁸O record, implying that both springtime temperature and the δ¹⁸O of sea water at 30 m depth around the Okinawa Islands have been stable for the past 3000 years at values similar to those of today. Moreover, we found one exceptionally light δ¹⁸O value from specimens spanning the past 250 years. The δ¹⁸O-derived temperature represents a departure of 2.1 °C from the average value for the past 250 years, being equal to the departure recorded during unusually high temperatures in the spring of 1998. This finding may imply that such high springtime sea surface temperature has been a rare event over the past 3000 years.  相似文献   

Field measurement and modeling of near-bed sediment transport processes with fluid mud layer in Tokyo Bay     

Yasuyuki Nakagawa  Kazuo Nadaoka  Hiroshi Yagi  Ryuichi Ariji  Haruo Yoneyama  Kazuhiro Shirai 《Ocean Dynamics》2012,62(10-12):1535-1544

Tokyo Bay is one of the estuaries in Japan with a high population of almost 26 million people in the basin area. One of the major concerns for the environment in this water area is the decreasing ecosystem functions including the deterioration of water and sediment qualities caused by various anthropogenic activities. Since the bottom sediments around almost the entire area of the inner bay consist of fine materials with a high organic content, which cause the deterioration of water quality through processes such as hypoxia, an understanding of the fine sediment dynamics in the Bay is crucial for an environmental assessment of the water area. This paper proposes a model for the key processes of fine sediment dynamics, which reflects field data about muddy bed structures and their dynamics obtained during the monitoring campaign in 2007. One of the specific features of the sediment in the Bay at present is the persistent existence of fluid mud layers (water content over 300?%) with a thickness of around a few decimeters, which might be caused by deposition of abundant organic particles due to eutrophication. The present study shows that diffusion flux model delivers quite reliable results for estimating erosion flux from the top of fluid mud layers after calibrating the model parameter against the time series data of vertical flux measured by an acoustic Doppler velocimeter system. This study also derives analytical solutions, based on the Bingham fluid concept, of advection flux in the fluid mud layer on which external shear stress force is applied.  相似文献   

Numerical study of three-dimensional shelf circulation on the Scotian Shelf using a shelf circulation model     

Kyoko Ohashi  Jinyu Sheng  Keith R. Thompson  Charles G. Hannah  Harold Ritchie 《Continental Shelf Research》2009

A numerical shelf circulation model was developed for the Scotian Shelf, using a nested-grid setup consisting of a three-dimensional baroclinic inner model embedded inside a two-dimensional barotropic outer model. The shelf circulation model is based on the Princeton Ocean Model and driven by three-hourly atmospheric forcing provided by a numerical weather forecast model and by tidal forcing specified at the inner model's open boundaries based on pre-calculated tidal harmonic constants. The outer model simulates the depth-mean circulation forced by wind and atmospheric pressure fields over the northwest Atlantic Ocean with a horizontal resolution of 1/12°. The inner model simulates the three-dimensional circulation over the Gulf of St. Lawrence, the Scotian Shelf, and the adjacent slope with a horizontal resolution of 1/16°. The performance of the shelf circulation model is assessed by comparing model results with oceanographic observations made along the Atlantic coast of Nova Scotia and in the vicinity of Sable Island (on the Scotian Shelf) during two periods: October 2000–March 2001 and April–June 2002. Analysis of model results on Sable Island Bank indicates that tidal currents account for as much as ∼80% of the total variance of near-bottom currents, and currents driven by local winds account for ∼30% of the variance of the non-tidal near-bottom currents. Shelf waves generated remotely by winds and propagating into the region also play an important role in the near-bottom circulation on the bank.  相似文献   

Symplectic integrators and their application to dynamical astronomy     

Hiroshi Kinoshita  Haruo Yoshida  Hiroshi Nakai 《Celestial Mechanics and Dynamical Astronomy》1990,50(1):59-71

Symplectic integrators have many merits compared with traditional integrators:  相似文献   

Changes of microbial populations in a ship's ballast water and sediments on a voyage from Japan to Qatar     

Mimura H  Katakura R  Ishida H 《Marine pollution bulletin》2005,50(7):751-757

Colony-forming eutrophic marine microorganisms in ballast water were counted in samples taken on board in 2002 and 2003. In the ballast water in Japan, viable cell numbers were highly variable but not by more than 10(5.1) colony-forming units (CFU)ml(-1) regardless of season. Even when ballast water was discharged offshore, values varied but not by more than 10(5.0) CFUml(-1). The effectiveness of the ballast water exchange was unconfirmed, except for the February 2003 voyage. No microbial colonies were counted in the reloaded ballast water in the high seas on that voyage, which contributed to the reduction of the total number of viable cells sampled in the discharged ballast water at the Ras Laffan port in Qatar. In sediment samples, the values of 10(5.2) - 10(6.0) CFUml(-1) were estimated for all seasons in which voyages took place. The maximum of the marine Vibrio species, 110 CFUml(-1), was observed in the ballast water sample taken in July 2003. The estimated total viable cell numbers in sediments were higher than those counted in the ballast water throughout the experiments, indicating the importance of sediment management as well as ballast water management on vessels traveling from Japan.  相似文献