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261.
262.
Wenjun Yong E. Dachs A. C. Withers E. J. Essene 《Physics and Chemistry of Minerals》2007,34(2):121-127
A multi-anvil device was used to synthesize 24 mg of pure γ-Fe2SiO4 crystals at 8.5 GPa and 1,273 K. The low-temperature heat capacity (C
p) of γ-Fe2SiO4 was measured between 5 and 303 K using the heat capacity option of a physical properties measurement system. The measured
heat capacity data show a broad λ-transition at 11.8 K. The difference in the C
p between fayalite and γ-Fe2SiO4 is reduced as the temperature increases in the range of 50–300 K. The gap in C
p data between 300 and 350 K of γ-Fe2SiO4 is an impediment to calculation of a precise C
p equation above 298 K that can be used for phase equilibrium calculations at high temperatures and high pressures. The C
p and entropy of γ-Fe2SiO4 at standard temperature and pressure (S°298) are 131.1 ± 0.6 and 140.2 ± 0.4 J mol−1 K−1, respectively. The Gibbs free energy at standard pressure and temperature (ΔG°
f,298) is calculated to be −1,369.3 ± 2.7 J mol−1 based on the new entropy data. The phase boundary for the fayalite–γ-Fe2SiO4 transition at 298 K based on current thermodynamic data is located at 2.4 ± 0.6 GPa with a slope of 25.4 bars/K, consistent
with extrapolated results of previous experimental studies. 相似文献
263.
264.
通过对厦门市1989年、1993年、1997年TM遥感影像和2003年ETM+遥感影像的解译分析统计,用单一土地利用动态度、转移矩阵等对1989-2003年厦门市湿地动态变化进行了分析,并进行了主要驱动力分析。结果表明:1989-2003年间,由于经济发展、人口增长以及农业生产比较利益的驱动和农业内部结构调整的影响,水库水塘、养殖、滩涂等湿地类型被非湿地侵占;养殖面积从1989年的4230hm2持续增加到2003年的9768hm2,主要是通过占用非湿地、滩涂、盐田和水库水塘增加的;红树林面积大幅度减少,从1989年的84hm2持续减少到2003年的17hm2,主要是由于养殖、非湿地的侵占以及遭受破坏变为滩涂。 相似文献
265.
266.
The 0S2~0S54 spheroidal modes of Earth’s free oscillations, triggered by the great Sumatra-Andaman earthquake of 26 December 2004 are retrieved from VHZ data recorded by seven upgraded stations of China Digital Seismograph Network (CDSN). We compare these spheroidal modes with theoretical free oscillation spectra calculated from the Preliminary Reference Earth Model (PREM) and find a coincidence between their periods. Spectral splitting phenomenon is observed obviously in 0S2, 0S3, 0S4, 2S1 and 1S2 free oscillation modes. What is most noticeable is that the oscillation mode 2S1 is reported for the second time (the first time by Rosat et al) without any data stacking. We simulated the split singlet of 0S2 mode on seven CDSN stations based on general focal mechanism and seismic moment of the earthquake. The result shows that seismic moment of the earthquake can reach 1023 N.m. We also find that the recording of Earth’s free oscillations carries abundant information of source mechanism and earthquake location, which is applicable to the detailed study of source rupture parameters. 相似文献
267.
A time-domain method for the analysis of arch dam-foundation rock dynamic interaction during earthquake was proposed, and
the dynamic relaxation technique was adopted to obtain the initial static response for dynamic analysis by [Du et al. (2005).
The paper has been contributed to Bulletin of earthquake engineering]. In this paper, a nonlinear explicit method in time
domain considering the opening and closing effect of contact joints on arch dam during earthquake is further proposed by introducing
the dynamic contact force model into the method. The simulation accuracy of dynamic contact force model is verified by comparing
its calculation result and test result of scale model on shaking table. Finally, the influence of joints on the seismic response
of Xiaowan arch dam is studied by the proposed method and some conclusions are given. 相似文献
268.
This study is concerned with the influence of the glacial-isostatic adjustment caused by the last Pleistocene deglaciation
on the present-day sea level. The viscoelastic deformation caused by the time-variable ice and ocean loads is simulated by
computing the resulting perturbations for a spherical, self-gravitating, incompressible, Maxwell-viscoelastic earth model.
The associated variation of the earth rotation is described in terms of the Liouville equation, which is solved by means of
the MacCullagh formulae. This allows the determination of the vertical displacement and geoid height and, thus, the solution
of the sea-level equation. We test several viscosity and ice models and evaluate them by comparison of the computed response
with the Holocene relative sea-level record. Using the optimum combination of viscosity and ice models, we then estimate the
influence of the last Pleistocene deglaciation on the tide-gauge measurements. A comparison between the observational and
residual linear trends for the tide-gauge measurements shows a significant reduction of the variance and geographical variability
for the latter, in particular for the formerly ice-covered regions of North America and Scandinavia. The favoured value determined
for the global mean sea-level rise is (1.46±0.2) mm a−1. 相似文献
269.
介绍用带权约束平差原理编制的工程控制网试验修正法设计和平差程序,并用于设计工程导线和平差变形观测控制网等实际工程的例子,据此提供一些结论和建议. 相似文献
270.
GIS中地籍宗地面积的方差分量估计 总被引:2,自引:0,他引:2
探讨在地籍宗地数字化的面积处理问题中,把已知面积数据和数字化坐标同时作为观测值的面积处理方法.采用方差分量估计,解决已知面积数据参与平差时的权的确定.通过实例分析,认为采用条件平差方差分量估计方法来对宗地面积处理,能够更加合理地调整已有面积与由数字化坐标得到的面积值之间的差异. 相似文献