Equation of state of iron–silicon alloys to megabar pressure

The stability and pressure–volume equation of state of iron–silicon alloys, Fe-8.7 wt% Si and Fe-17.8 wt% Si, have been investigated using diamond-anvil cell techniques up to 196 and 124 GPa, respectively. Angular–dispersive X-ray diffractions of iron–silicon alloys were measured at room temperature using monochromatic synchrotron radiation and an imaging plate (IP). A bcc–Fe-8.7 wt% Si transformed to hcp structure at around 1636 GPa. The high-pressure phase of Fe-8.7 wt% Si with hexagonal close-packed (hcp) structure was found to be stable up to 196 GPa and no phase transition of bcc–Fe-17.8 wt% Si was observed up to 124 GPa. The pressure–volume data were fitted to a third-order Birch–Murnaghan equation of state (BM EOS) with zero–pressure parameters: V₀=22.2(8) ų, K₀=198(9) GPa, and K₀=4.7(3) for hcp–Fe-8.7 wt% Si and V₀=179.41(45) ų, K₀=207(15) GPa and K₀=5.1(6) for Fe-17.8 wt% Si. The density and bulk sound velocity of hcp–Fe-8.7 wt% Si indicate that the inner core could contain 3–5 wt% Si.     

Thermal equation of state of majorite with MORB composition

In situ synchrotron X-ray diffraction experiments were conducted using the SPEED-1500 multi-anvil press at SPring-8 on majoritic garnet synthesized from natural mid-ocean ridge basalt (MORB), whose chemical composition is close to the average of oceanic crust, at 19 GPa and 2200 K. Pressure-volume-temperature data were collected using a newly developed high-pressure cell assembly to 21 GPa and 1273 K. Data were fit to the high-temperature Birch-Murnaghan equation of state, with fixed values for the ambient cell volume (V₀ = 1574.14(4) Å³) and the pressure derivative of the isothermal bulk modulus (K^′T = 4). This yielded an isothermal bulk modulus of K_T0 = 173(1) GPa, a temperature derivative of the bulk modulus (∂K_T/∂T)_P = −0.022(5) GPa K⁻¹, and a volumetric coefficient of thermal expansivity α = a + bT with values of a = 2.0(3) × 10⁻⁵ K⁻¹ and b = 1.0(5) × 10⁻⁸ K⁻². The derived thermoelastic parameters are very similar to those of pyrope. The density of subducted oceanic crust compared to pyrolitic mantle at the conditions in Earth's transition zone (410-660 km depth) was calculated using these results and previously reported thermoelastic parameters for MORB and pyrolite mineral assembledges. These calculations show that oceanic crust is denser than pyrolitic mantle throughout the mantle transition zone along a normal geotherm, and the density difference is insensitive to temperature at the pressures in lower part of the transition zone.     

Stability and P–V–T equation of state of KAlSi3O8-hollandite determined by in situ X-ray observations and implications for dynamics of subducted continental crust material

In situ X-ray diffraction measurements of KAlSi₃O₈-hollandite (K-hollandite) were performed at pressures of 15–27 GPa and temperatures of 300–1,800 K using a Kawai-type apparatus. Unit-cell volumes obtained at various pressure and temperature conditions in a series of measurements were fitted to the high-temperature Birch-Murnaghan equation of state and a complete set of thermoelastic parameters was obtained with an assumed K′_300,0=4. The determined parameters are V _300,0=237.6(2) Å³, K _300,0=183(3) GPa, (?K _T,0/?T) _P =?0.033(2) GPa K^?1, a ₀=3.32(5)×10^?5 K^?1, and b ₀=1.09(1)×10^?8 K^?2, where a ₀ and b ₀ are coefficients describing the zero-pressure thermal expansion: α _T,0 = a ₀ + b ₀ T. We observed broadening and splitting of diffraction peaks of K-hollandite at pressures of 20–23 GPa and temperatures of 300–1,000 K. We attribute this to the phase transitions from hollandite to hollandite II that is an unquenchable high-pressure phase recently found. We determined the phase boundary to be P (GPa)=16.6 + 0.007 T (K). Using the equation of state parameters of K-hollandite determined in the present study, we calculated a density profile of a hypothetical continental crust (HCC), which consists only of K-hollandite, majorite garnet, and stishovite with 1:1:1 ratio in volume. Density of HCC is higher than the surrounding mantle by about 0.2 g cm^?3 in the mantle transition zone while this relation is reversed below 660-km depth and HCC becomes less dense than the surrounding mantle by about 0.15 g cm^?3 in the uppermost lower mantle. Thus the 660-km seismic discontinuity can be a barrier to prevent the transportation of subducted continental crust materials to the lower mantle and the subducted continental crust may reside at the bottom of the mantle transition zone.     

优化偏最小二乘光度法同时测定铑铱钯的研究

采用局部加权、随机矩阵法等步骤,使建立的校准模型能充分反映未知样品的数字结构特征,达到优化的目的,从而改善偏最小二乘法在处理实际未知样品数据时的解析能力,以提高计算结果的精度。用该优化偏最小二乘法对模拟地质样品中痕量贵金属Ｒｈ、Ｉｒ、Ｐｄ进行多组分光度测定,其分析结果的相对误差均小于１０％;分别测定９．５μｇ／Ｌ、３５．０μｇ／Ｌ、６６．０μｇ／Ｌ含量的Ｒｈ、Ｉｒ和Ｐｄ７次,其标准偏差Ｒｈ为０．２;Ｉｒ为１．１;Ｐｄ为２．０。     

未来气候变化对中国荒漠化的潜在影响

气候变化与荒漠化间的反馈机制已成为全球研究的重点问题之一 ,减缓温室气体增加与防治荒漠化也成为全球协同行动的领域。作为一个发展中国家 ,中国的荒漠化及其防治不仅影响到全球气候变化 ,同时气候变化对中国的荒漠化也会产生显著影响。文中采用全国 1914个气象站的数据作为基线数据 ,在根据植被区划图在青藏高原上对Thornthwaite方程做适当订正的基础上 ,选择未来两个具代表性的年份 (2 0 30年和 2 0 5 6年 )用HadCM 2模型来预测全球变化框架下中国未来荒漠化生物气候类型区的变化。结果表明 ,各生物气候类型区的面积基本上均呈增加的趋势 ,其中以亚湿润干旱区增加为主 ,半干旱区次之。与 1990年的 395 6 5 81万km2 的荒漠化生物气候类型区面积相比 ,在GHGs年增量为 1%且考虑硫酸盐溶胶影响的情况下 ,2 0 30年和 2 0 5 6年分别提高了 11 33%和12 94% ,而在GHGs年增量为 0 5 %且考虑硫酸盐溶胶影响的情况下 ,则分别提高了 3 75 %和6 95 % ,比前者分别减少了 7 5 8和 5 99个百分点。虽然在GHGs年增量 0 5 %的减少情况下 ,中国未来荒漠化生物气候类型区面积扩大和程度加剧的速度有所减缓 ,但其总体增加仍很显著。因此进一步开展气候变化与荒漠化间相互作用的研究 ,并用以指导中国的荒漠化防治工?     

宗地面积测量限差的探讨

作者结合工作实践,对地籍调查中宗地面积两次测绘限差分布规律进行了分析,对宗地面积测绘限差公式进行推导,该公式对实际工作有一定的参考作用。     

关于VTI介质中多分量转换波地震数据采集的最佳接收时窗

以P_P波时窗和P_SV波时窗的交叉部分作为VTI介质中P_P波、P_SV波联合采集的最佳时窗,在有效时窗内通过基于VTI介质的射线追踪法确定每个反射点的P_P波、P_SV波射线路径和相角,求解Zoeppritz方程得出P_SV波与P_P波反射系数(或透射系数)的比值,并将该比值的绝对值定义为控制因子G. 以G值作为控制VTI介质中P_P波、P_SV波联合采集观测系统设计的主要参数,通过分析G值确定检波器位置的最佳接收时窗,得出优化VTI介质中多分量转换波地震数据采集的接收时窗的方法.     

The Environmental benefits and costs of conservation tillage

 Every production practice, including conservation tillage, has positive or negative environmental consequences that may involve air, land, water, and/or the health and ecological status of wildlife. The negative impacts associated with agricultural production, and the use of conventional tillage systems in particular, include soil erosion, energy use, leaching and runoff of agricultural chemicals, and carbon emissions. Several of these impacts are quantified. The conclusions suggest that the use of conservation tillage does result in less of an adverse impact on the environment from agricultural production than does conventional tillage by reducing surface water runoff and wind erosion. Additionally, wildlife habitat will be enhanced to some extent with the adoption of conservation tillage and the benefits to be gained from carbon sequestration will depend on the soil remaining undisturbed. Finally, further expansion of conservation tillage on highly erodible land will unquestionably result in an increase in social benefits, but the expected gains will be modest.     

横向地震波冲击下建筑结构稳定性变化分析

高层EPS法分析横向地震波冲击下建筑结构稳定性变化时,未进行横向地震波随机过程数学模拟,获取的横向地震波与实测不符,提出一种新的横向地震波冲击下建筑结构稳定性变化分析方法,采用三角级数型非平稳随机过程模型函数,模拟横向地震波非平稳性特征,得到横向地震波模拟曲线,根据该曲线建立建筑结构稳定性动力运动方程,运用Hilber-Hughes-Taylor递推格式求解该方程的安全系数,安全系数越高建筑结构稳定性越强。为研究建筑结构在横向地震波反复荷载作用下的稳定性状态,运用弹塑性损伤模型模拟建筑结构核心筒墙体混凝土,得到用于分析建筑结构稳定性的最大、最小特征值。实验结果表明,所提方法能够分析建筑结构稳定性变化,横向地震波冲击前5 s对建筑结构稳定性影响最大。     

海洋结构物小尺度桩柱的水动力系数研究与进展

本文主要归纳了基于Morison方程求解小尺度桩柱的水动力系数方面的研究成果。分别从单桩柱和群桩两个方面对水动力系数的研究成果,包括纯波、波流混合、横向力、直立桩柱、倾斜桩柱、复杂结构桩柱、粗糙度等进行了阐述,给出了在波流条件下水动力系数的变化规律;归纳了当前水动力系数的求解方法;介绍了在水动力系数的物模实验、数值仿真以及实验数据处理方法上的研究进展,并提出了相关研究的建议。