Multiple parent bodies of ordinary chondrites     

Kiyoshi Yomogida  Takafumi Matsui 《Earth and Planetary Science Letters》1984,68(1):34-42

Thermal histories of chondrite parent bodies are calculated from an initial state with material in a powder-like form, taking into account the effect of consolidation state on thermal conductivity. The very low thermal conductivity of the starting materials makes it possible for a small body with a radius of less than 100 km to be heated by several hundred degrees even if long-lived radioactive elements in chondritic abundances are the only source of heat. The maximum temperature is determined primarily by the temperature at which sintering of the constituent materials occurs. The thermal state of the interior of a chondrite parent body after sintering has begun is nearly isothermal. Near the surface, however, where the material is unconsolidated and the thermal conductivity is much lower, the thermal gradient is quite large. This result contradicts the conventional “onion-shell” model of chondrite parent bodies. But because the internal temperature is almost constant through the whole body, it supports a “multiple-parent bodies” model, according to which each petrologic type of chondrite comes from a different parent body.  相似文献   

An Economical Approach to Determining the Extent of Ground-Water Contamination and Formulating a Contaminant Removal Plan     

Kiyoshi W. Mido 《Ground water》1981,19(1):41-47

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Resolution dependence of tropical cyclone formation in CMIP3 and finer resolution models   总被引：1，自引：0，他引：1  

Kevin Walsh  Sally Lavender  Enrico Scoccimarro  Hiroyuki Murakami 《Climate Dynamics》2013,40(3-4):585-599

Detection of tropical lows is performed in a suite of climate model simulations using objectively-determined detection thresholds that are resolution-dependent. It is found that there is some relationship between model resolution and tropical cyclone formation rate even after the resolution-dependent tropical cyclone detection threshold is applied. The relationship is investigated between model-simulated tropical cyclone formation and a climate-based tropical cyclone Genesis Potential Index (GPI). It is found that coarser-resolution models simulate the GPI better than they simulate formation of tropical cyclones directly. As a result, there appears to be little relationship from model to model between model GPI and the directly-simulated cyclone formation rate. Statistical analysis of the results shows that the main advantage of increasing model resolution is to give a considerably better pattern of cyclone formation. Finer resolution models also simulate a slightly better pattern of GPI, and for these models there is some relationship between the pattern of GPI simulated by each model and that model’s pattern of simulated tropical cyclone formation.  相似文献   

Will the South Asian monsoon overturning circulation stabilize any further?     

R. Krishnan  T. P. Sabin  D. C. Ayantika  A. Kitoh  M. Sugi  H. Murakami  A. G. Turner  J. M. Slingo  K. Rajendran 《Climate Dynamics》2013,40(1-2):187-211

Understanding the response of the South Asian monsoon (SAM) system to global climate change is an interesting scientific problem that has enormous implications from the societal viewpoint. While the CMIP3 projections of future changes in monsoon precipitation used in the IPCC AR4 show major uncertainties, there is a growing recognition that the rapid increase of moisture in a warming climate can potentially enhance the stability of the large-scale tropical circulations. In this work, the authors have examined the stability of the SAM circulation based on diagnostic analysis of climate datasets over the past half century; and addressed the issue of likely future changes in the SAM in response to global warming using simulations from an ultra-high resolution (20 km) global climate model. Additional sensitivity experiments using a simplified atmospheric model have been presented to supplement the overall findings. The results here suggest that the intensity of the boreal summer monsoon overturning circulation and the associated southwesterly monsoon flow have significantly weakened during the past 50-years. The weakening trend of the monsoon circulation is further corroborated by a significant decrease in the frequency of moderate-to-heavy monsoon rainfall days and upward vertical velocities particularly over the narrow mountain ranges of the Western Ghats. Based on simulations from the 20-km ultra high-resolution model, it is argued that a stabilization (weakening) of the summer monsoon Hadley-type circulation in response to global warming can potentially lead to a weakened large-scale monsoon flow thereby resulting in weaker vertical velocities and reduced orographic precipitation over the narrow Western Ghat mountains by the end of the twenty-first century. Supplementary experiments using a simplified atmospheric model indicate a high sensitivity of the large-scale monsoon circulation to atmospheric stability in comparison with the effects of condensational heating.  相似文献   

Formation of a solid solution in the MgSiO3–MnSiO3 perovskite system     

Lin Li  Takaya Nagai  Tomoki Ishido  Satoko Motai  Kiyoshi Fujino  Shoichi Itoh 《Physics and Chemistry of Minerals》2014,41(6):431-437

Experiments using laser-heated diamond anvil cells combined with synchrotron X-ray diffraction and SEM–EDS chemical analyses have confirmed the existence of a complete solid solution in the MgSiO₃–MnSiO₃ perovskite system at high pressure and high temperature. The (Mg, Mn)SiO₃ perovskite produced is orthorhombic, and a linear relationship between the unit cell parameters of this perovskite and the proportion of MnSiO₃ components incorporated seems to obey Vegard’s rule at about 50 GPa. The orthorhombic distortion, judged from the axial ratios of a/b and \( \sqrt{2}\,a/c, \) monotonically decreases from MgSiO₃ to MnSiO₃ perovskite at about 50 GPa. The orthorhombic distortion in (Mg_0.5, Mn_0.5)SiO₃ perovskite is almost unchanged with increasing pressure from 30 to 50 GPa. On the other hand, that distortion in (Mg_0.9, Mn_0.1)SiO₃ perovskite increases with pressure. (Mg, Mn)SiO₃ perovskite incorporating less than 10 mol% of MnSiO₃ component is quenchable. A value of the bulk modulus of 256(2) GPa with a fixed first pressure derivative of four is obtained for (Mg_0.9, Mn_0.1)SiO₃. MnSiO₃ is the first chemical component confirmed to form a complete solid solution with MgSiO₃ perovskite at the P–T conditions present in the lower mantle.  相似文献   

Monitoring of internal failure evolution in soils using computerization X-ray tomography   总被引：1，自引：0，他引：1  

B. Shi  Y. Murakami  Z. Wu  J. Chen  H. Inyang 《Engineering Geology》1999,54(3-4):321-328

Computerized X-ray tomography (CT) has been used in disciplines such as soil science, geology and rock mechanics to analyze the texture of geomaterials. However, this potentially useful method has not thus far been used adequately in engineering geological analyses.To investigate its feasibility, CT is utilized in this study to monitor the evolution of internal failure in soil masses. An apparatus that can be fitted into the chamber of a medical CT was built to conduct geotechnical tests. Loading and shearing experiments were performed on bentonite, kaolinite, sand, silicon powders, and glass beads. CT images have been taken on different cross-sections inside the specimens to monitor soil deformation continuously. The results of direct shear, horizontal and vertical loading tests are presented and discussed. It has been demonstrated that CT is a powerful non-destructive and non-invasive tool for engineering geological analyses.  相似文献   

Resolution Improvement of Solar Images     

Miura  Noriaki  Baba  Naoshi  Sakurai  Takashi  Ichimoto  Kiyoshi  Soltau  Dirk  Brandt  Peter 《Solar physics》1999,187(2):347-356

A method for the improvement of resolution in an observed solar image is proposed. A blind deconvolution method is used for restoration of an atmospherically-degraded solar image, and a super-resolution method is applied to its restored image to improve the resolution. It is confirmed that a blind deconvolution process can restore fine structures that are blurred in an observed image, and that the super-resolution process can make a cutoff frequency in a blind-deconvolved image higher. A time series of super-resolved images of a sunspot observed with the 70-cm Vacuum Tower Telescope at Teide Observatory is presented.  相似文献