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91.
M. Akaogi H. Takayama H. Kojitani H. Kawaji T. Atake 《Physics and Chemistry of Minerals》2007,34(3):169-183
The low-temperature isobaric heat capacities (C
p) of β- and γ-Mg2SiO4 were measured at the range of 1.8–304.7 K with a thermal relaxation method using the Physical Property Measurement System.
The obtained standard entropies (S°298) of β- and γ-Mg2SiO4 are 86.4 ± 0.4 and 82.7 ± 0.5 J/mol K, respectively. Enthalpies of transitions among α-, β- and γ-Mg2SiO4 were measured by high-temperature drop-solution calorimetry with gas-bubbling technique. The enthalpies of the α−β and β−γ
transitions at 298 K (ΔH°298) in Mg2SiO4 are 27.2 ± 3.6 and 12.9 ± 3.3 kJ/mol, respectively. Calculated α−β and β−γ transition boundaries were generally consistent
with those determined by high-pressure experiments within the errors. Combining the measured ΔH°298 and ΔS°298 with selected data of in situ X-ray diffraction experiments at high pressure, the ΔH°298 and ΔS°298 of the α−β and β−γ transitions were optimized. Calculation using the optimized data tightly constrained the α−β and β−γ transition
boundaries in the P, T space. The slope of α−β transition boundary is 3.1 MPa/K at 13.4 GPa and 1,400 K, and that of β−γ boundary 5.2 MPa/K at 18.7 GPa
and 1,600 K. The post-spinel transition boundary of γ-Mg2SiO4 to MgSiO3 perovskite plus MgO was also calculated, using the optimized data on γ-Mg2SiO4 and available enthalpy and entropy data on MgSiO3 perovskite and MgO. The calculated post-spinel boundary with a Clapeyron slope of −2.6 ± 0.2 MPa/K is located at pressure
consistent with the 660 km discontinuity, considering the error of the thermodynamic data. 相似文献
92.
93.
The soil-covered landscape surface can be idealized from two viewpoints. The intuitive view is of a smooth, absolutely continuous surface with continuous contour lines and measurable in integral dimensions. The alternative view emphasizes the roughness, a surface of little regularity and at the limit of no contours, the appropriate measure being that of fractional Hausdorff dimension. Regularity is a local property and both idealizations need to stop far short of the limit to avoid awkward consequences. The dichotomy of viewpoint can be matched in the theory of Gaussian random fields. These, if they are smooth, are very smooth but if they are irregular they are highly irregular (erratic); there is no middle ground. This Belayev dichotomy is defined and both modes applied to the soil-covered landscape. On the one hand, if the landscape is subject to a general diffusive type degradation or more generally a Davisian downwasting regime then the curvature of the landscape surface is progressively straightened and the distribution of gradient (increments) along a typical traverse will eventually adopt a Gaussian form. Then from the irregular viewpoint the surface is ultimately well represented by a fractional Brownian surface of low Hausdorff dimension (2·0 < dim < 2·3). The Hausdorff dimension is directly related to the entropy of the landscape and as degradation proceeds both quantities decrease in value. On the other hand, if the surface is regarded as smooth and well represented by an absolutely continuous Gaussian field then the mean value of the number of upcrossings of a level or the extent of an excursion set will also be Gaussian. This analysis is restricted to one dimension; the number of times a profile curve crosses or the amount of time it spends above any given level. Predictions from both viewpoints are substantially corroborated in a map analysis of 15 sites on varied terrains in Southern England and the map analysis checked against one based upon digital tape data for one of the sites. 相似文献
94.
断层形变短临前兆表现形式是多样的,并作了初步分类,丛集性高频波动是其一种重要现形式,探索了这种前兆信息的提取思路和方法,认为信息丛集度C是描述这种前兆短临信息,熵值积分平滑值G是描述中短信息较理想的特征量,震例学表明第二类前兆具有较好的预报效能,对异常判据了初步探索。 相似文献
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97.
关于熵与城市发展之探讨 总被引:5,自引:0,他引:5
城市的形成和发展是一个历史过程,如何评判城市是一个深刻的哲学命题,从熵定律角度来研究城市发展,可以帮助我们建立一种新的城市发展观。城市发展是一个不可逆过程,城市作为一个开放的系统,只要能够从外部环境得到足够的负熵流以抵消内部的熵增,城市将形成耗散结构系统并朝着进化的方向发展。未来的城市应进入低熵社会,主要途径是:建立生态城市,走可持续发展的道路;建立数字城市,实现城市社会信息化;控制城市人口,合理发展城市规模。 相似文献
98.
SAR影像与TM影像的几种融合处理方法 总被引:13,自引:2,他引:11
利用彩色空间变换、比值变换及相关系数法分别对SAR影像与TM3 、TM4 、TM5 三波段影像进行融合处理。文章介绍了影像融合中的具体技术问题及其处理方法。因侧视雷达图像一般有明显的孤立噪声,所以,在进行影像融合处理之前,先对SAR影像进行预处理,文中用δ滤波法抑制孤立噪声(光斑) .最后,从视觉效果、熵、平均梯度值以及标准差等4 方面评价了影像融合的质量。 相似文献
99.
Based on the body strain observation data at Liyang and Xuzhou stations, the Correlation Dimension D2 and the second-order Renyi entropy K2 of the attractor are calculated and studied. In addition, a new method of evaluating the longest predictable time of precursor attractor is advanced under the condition of a certain anomalous criterion rule. The conclusion indicates that the body strain precursor attractor is one of the chaotic attractors and it has some determinate change rules such as the dimension declines before an earthquake and the number of the independent factors on which the variation of the system depends is within the range of 5 - 12. The conclusion also indicates that the longest evaluated predictable time of the body strain attractor is 213 days at the Liyang station and 342 days at the Xuzhou station. It is clear that this research can be of great reference value for recognizing the nonlinear behavior of precursor attractors and for evaluating the predictability of different precursor 相似文献
100.
基于贝叶斯最大熵的甘肃省多年平均降水空间化研究 总被引:1,自引:0,他引:1
贝叶斯最大熵方法可以对具有一定不确定性的“软数据”和认为没有误差的“硬数据”进行插值。对甘肃省1961—1990年52个气象站点的多年平均降水数据进行空间化研究。通过比较普通克里格、共协克里格、三元回归建模后残差插值以及基于贝叶斯最大熵的3种不同软硬数据参与情况下的插值结果,发现考虑降水30 a时间序列不完整性以及辅助变量经验模型不确定性的插值结果的MAE和RMSE,比直接使用多年平均降水数据直接插值的MAE和RMSE小,表明贝叶斯最大熵方法通过对不确定性的考虑可以有效降低预测结果的绝对误差。从降水的空间分布来看,考虑辅助变量DEM的插值结果能相对较好的体现高程对降水的地形影响,尤其分区将辅助变量转换为软数据可以有效体现不同区域高程对降水的不同影响问题。综合误差评价以及降水插值结果的空间分布,认为BME插值过程中可以考虑数据本身以及辅助数据利用的不确定性,使降水空间化的结果更加真实客观,同时为合理利用辅助信息提供了一个新思路。 相似文献