A new high-pressure phase of strontium carbonate     

Shigeaki Ono  Miki Shirasaka  Takumi Kikegawa  Yasuo Ohishi 《Physics and Chemistry of Minerals》2005,32(1):8-12

High-pressure and high-temperature experiments conducted in a laser-heated diamond-anvil cell with a synchrotron X-ray diffraction method have revealed a phase transformation in the aragonite-type SrCO₃ at pressures above 10 GPa. The new phase has an orthorhombic symmetry and was confirmed to remain stable to 32 GPa. The Birch-Murnaghan equation of state for new phase was determined from the experimental unit cell parameters, with K₀ = 101 (± 16) GPa, K₀ = 4 (constrained value), and V₀ = 111.9 (± 2.2). This transformation in SrCO₃ is different from that in BaCO₃ as reported in previous studies. After decompression at ambient pressure, the high-pressure phase transforms to a metastable structure, which has an orthorhombic symmetry. This result should also resolve a dispute regarding the stable high-pressure phases in BaCO₃, which is an analog material of CaCO₃ and SrCO₃.This revised version was published in February 2005 with corrections to the Introduction and to the References.  相似文献   

Development of a Multi-Layer Urban Canopy Model for the Analysis of Energy Consumption in a Big City: Structure of the Urban Canopy Model and its Basic Performance   总被引：4，自引：0，他引：4  

Hiroaki?KondoEmail author  Yutaka?Genchi  Yukihiro?Kikegawa  Yukitaka?Ohashi  Hiroshi?Yoshikado  Hiroshi?Komiyama 《Boundary-Layer Meteorology》2005,116(3):395-421

A multilayer one-dimensional canopy model was developed to analyze the relationship between urban warming and the increase in energy consumption in a big city. The canopy model, which consists of one-dimensional diffusion equations with a drag force, has three major parameters: building width, distance between buildings, and vertical floor density distribution, which is the distribution of a ratio of the number of the buildings that are taller than some level to all the buildings in the area under consideration. In addition, a simplified radiative process in the canopy is introduced. Both the drag force of the buildings and the radiative process depend on the floor density distribution. The thermal characteristics of an urban canopy including the effects of anthropogenic heat are very complicated. Therefore, the focus of this research is mainly on the basic performance of an urban canopy without anthropogenic heat. First, the basic thermal characteristics of the urban canopy alone were investigated. The canopy model was then connected with a three-dimensional mesoscale meteorological model, and on-line calculations were performed for 10 and 11 August, 2002 in Tokyo, Japan. The temperature near the ground surface at the bottom of the canopy was considerably improved by the calculation with the canopy model. However, a small difference remained between the calculation and the observation for minimum temperature. Deceleration of the wind was well reproduced for the velocity at the top of the building by the calculation with the canopy model, in which the floor density distribution was considered.  相似文献   

Nonlinear wave effect on the slow drift motion of a floating body   总被引：1，自引：0，他引：1  

Takumi Ohyama  John R. C. Hsu 《Applied Ocean Research》1995,17(6):349-362

The slow drift motion of a floating body in a two-dimensional wave field has been investigated using a time-domain, fully nonlinear numerical model with non-reflective open boundaries. Preliminary computations were conducted for incident bichromatic waves, in which wave theories with different orders were applied in generating the waves required. The results show that the use of low-order theories generates undesirable free waves, and that fourth-order terms contribute markedly to low-frequency input. The motion of a rectangular floating body in response to nonlinear bichromatic waves was computed. The numerical results for small-amplitude incident waves agree reasonably well with the second-order approximation for both the steady and difference-frequency (Δσ) components in the body's motion. For relatively large waves, however, the 2Δσ component becomes predominant compared with the Δσ component. The motion of the body in irregular waves with different wave parameters has also been presented in order to discuss the validity range of a second-order approximation.  相似文献   

越南东北部Cat Ba岛泥盆系-石炭系过渡层的初探     

Toshifumi KOMATSU  Reishi TAKASHIMA  TA Hoa PHUONG  Tran Huyen DANG  Duc Phong NGUYEN  Huu Hung NGUYEN  Satoru KATO  Kento HIRATA  Takumi MAEKAWA 《地球学报》2012,33(S1):38-38

The Pho Han Formation is exposed on southern Cat Ba Island, Hai Phong Province in northeastern Vietnam, and intercalates the Devonian and Carbonif-erous (D-C) boundary (Ta and Doan, 2007; Komatsu et al., 2012). The D-C boundary section consists mainly of limestone beds, numbered from 1 to 167, interca-lated with alternating black organic-rich shales. The limestone yields abundant brachiopods, crinoid-stems and conodonts. Preliminary investigations on strati-graphy (conodont biostratigraphy and δ13C) and sedi-mentology of beds 113-133 were undertaken in this study.  相似文献   

Reaction of forsterite with hydrogen molecules at high pressure and temperature     

Ayako?ShinozakiEmail author  Hisako?Hirai  Hiroyuki?Kagi  Tadashi?Kondo  Taku?Okada  Daisuke?Nishio-Hamane  Shin-ichi?Machida  Tetsuo?Irifune  Takumi?Kikegawa  Takehiko?Yagi 《Physics and Chemistry of Minerals》2012,39(2):123-129

High pressure and temperature reactions of a mixture of forsterite and hydrogen molecules have been carried out using a laser heated diamond anvil cell at 9.8–13.2 GPa and ~1,000 K. In situ X-ray diffraction measurements showed no sign of decomposition or phase transitions of the forsterite under these experimental conditions, indicating that the olivine structure was maintained throughout all runs. However, a substantial expansion of the unit cell volume of the forsterite was observed for samples down to ~3 GPa upon quenching to ambient pressure at room temperature. The Raman spectroscopy measurements under pressure showed significant shifts of the Raman peaks of the Si–O vibration modes for forsterite and of the intramolecular vibration mode for H₂ molecules toward a lower frequency after heating. Additionally, no OH vibration modes were observed by Raman and FT-IR spectroscopic measurements. These lines of evidence show that the observed volume expansion in forsterite is not explained by the incorporation of hydrogen atoms as hydroxyl, but suggest the presence of hydrogen as molecules in the forsterite structure under these high pressure and temperature conditions.  相似文献   

Density measurements of liquid Fe–Si alloys at high pressure using the sink–float method     

Ryuji Tateyama  Eiji Ohtani  Hidenori Terasaki  Keisuke Nishida  Yuki Shibazaki  Akio Suzuki  Takumi Kikegawa 《Physics and Chemistry of Minerals》2011,38(10):801-807

The compositional dependence on the density of liquid Fe alloys under high pressure is important for estimating the amount of light elements in the Earth’s outer core. Here, we report on the density of liquid Fe–Si at 4 GPa and 1,923 K measured using the sink–float method and our investigation on the effect of the Si content on the density of the liquid. Our experiments show that the density of liquid Fe–Si decreases from 7.43 to 2.71 g/cm³ non-linearly with increasing Si content (0–100 at%). The molar volume of liquid Fe–Si calculated from the measured density gradually decreases in the compositional range 0–50 at% Si, and increases in the range 50–100 at% Si. It should be noted that the estimated molar volume of the alloys shows a negative volume of mixing between Fe and Si. This behaviour is similar to Fe–S liquid (Nishida et al. in Phys Chem Miner 35:417–423, 2008). However, the excess molar volume of mixing for the liquid Fe–Si is smaller than that of liquid Fe–S. The light element contents in the outer core estimated previously may be an underestimation if we take into account the possible negative value of the excess mixing volume of iron–light element alloys in the outer core.  相似文献   

Temperature Variation in the Urban Canopy with Anthropogenic Energy Use   总被引：5，自引：0，他引：5  

H. Kondo  Y. Kikegawa 《Pure and Applied Geophysics》2003,160(1-2):317-324

  相似文献   

Compressibility of the calcium aluminosilicate, CAS, phase to 44 GPa     

Shigeaki Ono  Tsuyoshi Iizuka  Takumi Kikegawa 《Physics of the Earth and Planetary Interiors》2005,150(4):331-338

In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch–Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of ρ₀ = 3.888 g/cm³ and a bulk modulus of K₀ = 229 ± 9 GPa for K^′₀ = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at K^′₀ = 4, then the value of K₀ = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase.  相似文献   

An assessment of uncertainties in VS profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials     

Asten  Michael W.  Yong  Alan  Foti  Sebastiano  Hayashi  Koichi  Martin  Antony J.  Stephenson  William J.  Cassidy  John F.  Coleman  Jacie  Nigbor  Robert  Castellaro  Silvia  Chimoto  Kosuke  Cornou  Cécile  Cho  Ikuo  Hayashida  Takumi  Hobiger  Manuel  Kuo  Chun-Hsiang  Macau  Albert  Mercerat  E. Diego  Molnar  Sheri  Pananont  Passakorn  Pilz  Marco  Poovarodom  Nakhorn  Sáez  Esteban  Wathelet  Marc  Yamanaka  Hiroaki  Yokoi  Toshiaki  Zhao  Don 《Journal of Seismology》2022,26(4):757-780

Journal of Seismology - Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site...  相似文献   

Softening effects of RC nonstructural flat walls on ductile concrete buildings          下载免费PDF全文

Yasushi Sanada  Rokhyun Yoon  Takumi Akahori  Yuto Ojio  Ho Choi  Yousok Kim 《地震工程与结构动力学》2017,46(10):1645-1665

Nonstructural reinforced concrete flat walls architecturally designed as exterior/partition walls in concrete buildings were severely damaged by the 2011 earthquake off the Pacific coast of Tohoku. This damage was observed in the monolithic nonstructural flat walls of relatively old ductile concrete buildings. Although these flat walls might affect the overall seismic performance and behavior of a building, the nonstructural wall effects have not been clarified because of the complex interactions among the structural components. To understand these effects, this paper conducts an experimental and numerical investigation of the nonstructural wall effects, focusing on a typical residential building damaged by the 2011 earthquake. A single‐story, one‐bay moment‐resisting frame model of the building with a nonstructural flat wall was tested to clarify the fundamental behavior. The results reveal that the wall significantly contributed to the seismic performance of the overall frame until it failed in shear, subsequently losing structural effectiveness. Such experimental wall behavior could be simulated by the isoparametric element model. Moreover, the structural effects of the nonstructural flat walls on the global seismic performance and behavior of the investigated building were discussed through earthquake response analyses using ground motions recorded near the building site and pushover analyses. Consequently, the building damage could be simulated in an analytical case considering the nonstructural flat walls, showing larger inter‐story drifts in the lower stories due to softening of the walls. The analytical results also indicated that the softening of the nonstructural flat walls decreased the building ductility, as defined by ultimate inter‐story drifts. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献