地球偏心眼

我们人的心脏长在胸腔的中部,稍偏左方,呈圆锥形,大小约跟本人的拳头相等。那么,地球的心脏是怎样的呢？地球的心脏——地核,分为内外两层,外地核呈液态,而内地核则是铁镍成分的固态。     

晶体的热力学行为研究

在德拜模型的基础上研究晶体的热力学行为．德拜模型频谱函数在高频区与实验曲线相比偏差较大，对此，我们认为在高频区声子间的相互碰撞不能忽略，并对德拜近似模型作了一定修正，所求出的频谱函数在高频区能更好地接近实验曲线和反映频谱变化规律，用修正后的模型计算晶体的热容量与德拜模型保持一致，能很好地与实验结果符合．     

考虑物态变化的六参数砂土本构模型

以往的大多数砂土本构模型仅采用相对密度作指标,把初始密度不同的砂土当作不同的材料,需采用多组不同的材料参数。本文基于状态参数概念,提出了一个数学描述简单、仅有6个材料参数的砂土本构模型。该模型能够同时考虑相对密度和有效围压两个因素对材料物态变化的影响,并只用一组材料参数即可描述较大的围压和密度范围内砂土的排水应力应变响应。通过不同围压和初始密度条件下的三轴排水试验结果与数值模拟结果的对比,初步验证了模型的有效性。     

正弦电磁场作用下介质吸波特性研究

微波技术广泛用于无线通信、材料处理和材料介电常数测量等领域.微波处理材料的优点是传热快、体积加热、选择性加热、无环境污染和容易自动控制.作者描述了正弦电磁场与介质相互作用时的加热机理.对德拜型和非德拜型弛豫介质,导出了其介质吸波特性的计算模型Pd=21ωε″E2 21E2(cos2ωtεt′ cosωtsinωtεt″更重要的是,此模型甚至可用于解释微波辐照下材料发生的瞬态过程.     

固体理论中德拜态密度的两种推导

利用狄拉克δ函数和统计理论,分别计算态密度在德拜模型下的表达式.结果表明,这两种运算方法所得到的德拜态密度结果完全相同.     

高温下爱因斯坦模型与德拜模型热容结果的一致性

指出了高温下晶格振动热容理论中爱因斯坦模型与德拜模型的异同之处．理论分析发现，高温下晶格振动能与振动模式近似无关．解释了在相去甚远的假设前提下，两种晶格振动热容理论模型的结果在高温下一致的原因．     

反演地球模型中的介质参数

本回顾了地球物理反演发展的概况，介绍了作近几年来在这方面取得的主要成果，指出了进一步研究的方向。     

基于状态空间方程的油纸绝缘系统等效电路参数辨识

合理地辨识油纸绝缘系统等效电路的参数是绝缘老化特性分析的基础.根据回复电压测试原理,提出建立回复电压时域响应的状态空间模型,并利用控制理论中状态空间方程的求解方法结合自适应粒子群算法搜索出最优解,从而得到等效电路的未知参数值.利用国外学者所提供的一组300 MV·A油纸绝缘变压器不同充电时间下的回复电压响应曲线进行辨识,并将辨识结果所对应的回复电压曲线与测量曲线对比,二者重合度高,验证了计算模型及辨识方法的有效性.同时,分析了模型支路数不同时对辨识结果的影响,初步得出该台变压器选择6条支路辨识拟合效果最佳的结论.为油纸绝缘系统等值电路参数的辨识提供了一种新思路.     

试论德拜模型与固体热容量的关系

文章通过对德拜模型的研究，分析了利用德拜模型解决金属固体热容量与实验结果不一致的原因，并且研究了金属自由电子气对热容量的贡献．最终达到了由统计理论得到的金属固体热容量与实验结果一致的结论．     

地核为什么要燃烧？燃烧完地球会怎么样？

A：用燃烧这个词只是形象地表示地核内部温度很高（内部大概4500℃），并非我们常说的燃烧。早期的学说认为，地球在形成之初是团炽热的液体，后来慢慢冷却形成了固态的地壳，而核心仍然保持高温液态。     

地核物质的状态方程和参数

 解释了3种地核物质状态方程的异同,验证了Vinet et al. EOS(equation of state)比Shanker et al.EOS更接近Stacy EOS的结论,后者与高压极限的热动力学一致、而且与来源于地震波的数据完全匹配;同时与地震波测量数据进行了对照;给出了内核边界压力下物质摩尔体积随温度的变化函数,预言了密度亏损的温度变化.这对于揭示地球深部物质特性、研究地核内的轻物质组分以及深部动力学原理具有重要意义.     

Stability of the body-centred-cubic phase of iron in the Earth's inner core

Iron is thought to be the main constituent of the Earth's core, and considerable efforts have therefore been made to understand its properties at high pressure and temperature. While these efforts have expanded our knowledge of the iron phase diagram, there remain some significant inconsistencies, the most notable being the difference between the 'low' and 'high' melting curves. Here we report the results of molecular dynamics simulations of iron based on embedded atom models fitted to the results of two implementations of density functional theory. We tested two model approximations and found that both point to the stability of the body-centred-cubic (b.c.c.) iron phase at high temperature and pressure. Our calculated melting curve is in agreement with the 'high' melting curve, but our calculated phase boundary between the hexagonal close packed (h.c.p.) and b.c.c. iron phases is in good agreement with the 'low' melting curve. We suggest that the h.c.p.-b.c.c. transition was previously misinterpreted as a melting transition, similar to the case of xenon, and that the b.c.c. phase of iron is the stable phase in the Earth's inner core.     

外地核物质的状态参数方程

 在整个外地核空间内流体的对流存在狭窄的上升流通道(浮力团块上升至顶部)和宽阔的下降流通道(周围液体缓慢下降),假定这种对流循环相当快,以至于外地核接近于一个混合良好的等熵态,而各种物理量的偏离可以看作等熵态下的微扰.根据这一对流模型给出了外地核内下降部分物质的组分、温度、压力等状态参数的空间变化方程,以及与之密切相关的径向流体速度方程,并定性分析了各参量对外地核下降流体分层稳定性的贡献.     

Elasticity of iron at the temperature of the Earth's inner core.

Seismological body-wave and free-oscillation studies of the Earth's solid inner core have revealed that compressional waves traverse the inner core faster along near-polar paths than in the equatorial plane. Studies have also documented local deviations from this first-order pattern of anisotropy on length scales ranging from 1 to 1,000 km (refs 3, 4). These observations, together with reports of the differential rotation of the inner core, have generated considerable interest in the physical state and dynamics of the inner core, and in the structure and elasticity of its main constituent, iron, at appropriate conditions of pressure and temperature. Here we report first-principles calculations of the structure and elasticity of dense hexagonal close-packed (h.c.p.) iron at high temperatures. We find that the axial ratio c/a of h.c.p. iron increases substantially with increasing temperature, reaching a value of nearly 1.7 at a temperature of 5,700 K, where aggregate bulk and shear moduli match those of the inner core. As a consequence of the increasing c/a ratio, we have found that the single-crystal longitudinal anisotropy of h.c.p. iron at high temperature has the opposite sense from that at low temperature. By combining our results with a simple model of polycrystalline texture in the inner core, in which basal planes are partially aligned with the rotation axis, we can account for seismological observations of inner-core anisotropy.     

The plastic deformation of iron at pressures of the Earth's inner core

Soon after the discovery of seismic anisotropy in the Earth's inner core, it was suggested that crystal alignment attained during deformation might be responsible. Since then, several other mechanisms have been proposed to account for the observed anisotropy, but the lack of deformation experiments performed at the extreme pressure conditions corresponding to the solid inner core has limited our ability to determine which deformation mechanism applies to this region of the Earth. Here we determine directly the elastic and plastic deformation mechanism of iron at pressures of the Earth's core, from synchrotron X-ray diffraction measurements of iron, under imposed axial stress, in diamond-anvil cells. The epsilon-iron (hexagonally close packed) crystals display strong preferred orientation, with c-axes parallel to the axis of the diamond-anvil cell. Polycrystal plasticity theory predicts an alignment of c-axes parallel to the compression direction as a result of basal slip, if basal slip is either the primary or a secondary slip system. The experiments provide direct observations of deformation mechanisms that occur in the Earth's inner core, and introduce a method for investigating, within the laboratory, the rheology of materials at extreme pressures.     

Thermal and electrical conductivity of iron at Earth's core conditions

The Earth acts as a gigantic heat engine driven by the decay of radiogenic isotopes and slow cooling, which gives rise to plate tectonics, volcanoes and mountain building. Another key product is the geomagnetic field, generated in the liquid iron core by a dynamo running on heat released by cooling and freezing (as the solid inner core grows), and on chemical convection (due to light elements expelled from the liquid on freezing). The power supplied to the geodynamo, measured by the heat flux across the core-mantle boundary (CMB), places constraints on Earth's evolution. Estimates of CMB heat flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. These quantities remain poorly known because of inherent experimental and theoretical difficulties. Here we use density functional theory to compute these conductivities in liquid iron mixtures at core conditions from first principles--unlike previous estimates, which relied on extrapolations. The mixtures of iron, oxygen, sulphur and silicon are taken from earlier work and fit the seismologically determined core density and inner-core boundary density jump. We find both conductivities to be two to three times higher than estimates in current use. The changes are so large that core thermal histories and power requirements need to be reassessed. New estimates indicate that the adiabatic heat flux is 15 to 16 terawatts at the CMB, higher than present estimates of CMB heat flux based on mantle convection; the top of the core must be thermally stratified and any convection in the upper core must be driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMB heat flow. Power for the geodynamo is greatly restricted, and future models of mantle evolution will need to incorporate a high CMB heat flux and explain the recent formation of the inner core.     

Melting of the Earth's inner core

The Earth's magnetic field is generated by a dynamo in the liquid iron core, which convects in response to cooling of the overlying rocky mantle. The core freezes from the innermost surface outward, growing the solid inner core and releasing light elements that drive compositional convection. Mantle convection extracts heat from the core at a rate that has enormous lateral variations. Here we use geodynamo simulations to show that these variations are transferred to the inner-core boundary and can be large enough to cause heat to flow into the inner core. If this were to occur in the Earth, it would cause localized melting. Melting releases heavy liquid that could form the variable-composition layer suggested by an anomaly in seismic velocity in the 150 kilometres immediately above the inner-core boundary. This provides a very simple explanation of the existence of this layer, which otherwise requires additional assumptions such as locking of the inner core to the mantle, translation from its geopotential centre or convection with temperature equal to the solidus but with composition varying from the outer to the inner core. The predominantly narrow downwellings associated with freezing and broad upwellings associated with melting mean that the area of melting could be quite large despite the average dominance of freezing necessary to keep the dynamo going. Localized melting and freezing also provides a strong mechanism for creating seismic anomalies in the inner core itself, much stronger than the effects of variations in heat flow so far considered.     

Fine-scale heterogeneity in the Earth's inner core

The seismological properties of the Earth's inner core have become of particular interest as we understand more about its composition and thermal state. Observations of anisotropy and velocity heterogeneity in the inner core are beginning to reveal how it has grown and whether it convects. The attenuation of seismic waves in the inner core is strong, and studies of seismic body waves have found that this high attenuation is consistent with either scattering or intrinsic attenuation. The outermost portion of the inner core has been inferred to possess layering and to be less anisotropic than at greater depths. Here we present observations of seismic waves scattered in the inner core which follow the expected arrival time of the body-wave reflection from the inner-core boundary. The amplitude of these scattered waves can be explained by stiffness variations of 1.2% with a scale length of 2 kilometres across the outermost 300 km of the inner core. These variations might be caused by variations in composition, by pods of partial melt in a mostly solid matrix or by variations in the orientation or strength of seismic anisotropy.     

试论交流铁芯线圈的铁损

论述了引起交流铁芯线圈在工作中铁损的原因，通过周密分析研究推导了计算铁 定量公式，并纠正了《日本实用电工讲座》译著中的错误结论。