Linear Magnetoconvection in Rotating Fluid Spheres Permeated by a Uniform Axial Magnetic Field

A linear analysis of thermally driven magnetoconvection is carried out with emphasis on its application to convection in the Earth's core. We consider a rotating and self-gravitating fluid sphere (or spherical shell) permeated by a uniform magnetic field parallel to the spin axis. In rapidly rotating cases, we find that five different convective modes appear as the uniform field is increased; namely, geostrophic, polar convective, magneto-geostrophic, fast magnetostrophic and slow magnetostrophic modes. The polar convective (P) and magneto-geostrophic (E) modes seem to be of geophysical interest. The P mode is characterized by such an axisymmetric meridional circulation that the fluid penetrates the equatorial plane, suggesting that generation of quadrapole from dipole fields could be explained by a linear process. The E mode is characterized by a few axially aligned columnar rolls which are almost two-dimensional due to a modified Proudman-Taylor theorem.     

Autunian age constrained by fold tests for paleomagnetic data from the Mezarif and Abadla basins (Algeria)

A paleomagnetic study has been conducted on a formation dated as Autunian in the Nekheila area (31.4°N, 1.5°W) in the Mezarif basin. ChRM was thermally isolated in 117 samples from seven sites. This ChRM (D = 131.8°, I = 15.7°, k = 196, α₉₅ = 3.8° after dip correction; corresponding pole 29.3°S, 56.4°E) is very similar to that obtained in the neighboring Abadla basin from a formation of the same age. Fold tests associated with progressive unfolding applied to the full merged data from the dated formations of these two basins clearly indicate that the magnetization acquisition predates the deformation, which is attributed to the last phase of the late-Hercynian. The magnetization in these basins is therefore primary or acquired just after deposition. For the African Apparent Polar Wander Path, the age of the paleomagnetic poles of the Autunian part is now confirmed by paleomagnetic test.     

The seismological picture of the inner core: structure and rotation

This paper presents a review of recent results concerning the structure and the rotation of the inner core, as inferred from seismological observations. We first focus on the apparent hemispherical pattern of the inner core structure, observed in both the anisotropy and the heterogeneity of the uppermost layers, whereas isotropic velocities seem to be homogeneous in a broad wavelength domain. Then we present results on the radial variations of the attenuation and its possible anisotropy, for which viscoelasticity and wave scattering provide complementary explanations. Linked to these results is a discussion about the detection of the PKJKP phase, which propagates as S-wave inside the inner core. Finally, the seismological observations of a possible inner core rotation are discussed; recent results seem to favour rotation rates below 0.2° yr^?1.     

Flight test results from a strapdown airborne gravity system

In June 1995, a flight test was carried out over the Rocky Mountains to assess the accuracy of airborne gravity for geoid determination. The gravity system consisted of a strapdown inertial navigation system (INS), two GPS receivers with zero baseline on the airplane and multiple GPS master stations on the ground, and a data logging system. To the best of our knowledge, this was the first time that a strapdown INS has been used for airborne gravimetry. The test was designed to assess repeatability as well as accuracy of airborne gravimetry in a highly variable gravity field. An east-west profile of 250 km across the Rocky Mountains was chosen and four flights over the same ground track were made. The flying altitude was about 5.5km, i.e., between 2.5 and 5.0km above ground, and the average flying speed was about 430km/h. This corresponds to a spatial resolution (half wavelength of cutoff frequency) of 5.07.0km when using filter lengths between 90 and 120s. This resolution is sufficient for geoid determination, but may not satisfy other applications of airborne gravimetry. The evaluation of the internal and external accuracy is based on repeated flights and comparison with upward continued ground gravity using a detailed terrain model. Gravity results from repeated flight lines show that the standard deviation between flights is about 2mGal for a single profile and a filter length of 120s, and about 3mGal for a filter length of 90s. The standard deviation of the difference between airborne gravity upward continued ground gravity is about 3mGal for both filter lengths. A critical discussion of these results and how they relate to the different transfer functions applied, is given in the paper. Two different mathematical approaches to airborne scalar gravimetry are applied and compared, namely strapdown inertial scalar gravimetry (SISG) and rotation invariant scalar gravimetry (RISG). Results show a significantly better performance of the SISG approach for a strapdown INS of this accuracy class. Because of major differences in the error model of the two approaches, the RISG method can be used as an effective reliability check of the SISG method. A spectral analysis of the residual errors of the flight profiles indicates that a relative geoid accuracy of 23cm over distances of 200km (0.1 ppm) can be achieved by this method. Since these results present a first data analysis, it is expected that further improvements are possible as more refined modelling is applied. Received: 19 August 1996 / Accepted: 12 May 1997     

地幔热力不稳定性分析

根据地幔热动力学模型,分析了地幔在多种因素（特别是地球自转效应）影响下的热力不稳定性条件和临界条件,结果表明,地质年代在影响地幔热力不稳定性的诸因素中,地幔内部的热源（放射性生热、相变生热、绝热压缩生热和底部加热）效应能够使地幔lavleish数增大,即增大地幔运动的动力;而地球的自转效应却能减小地幔运动的临界阻力,因此它们对地幔热力不稳定性都具激发作用,而对地幔粘滞性和热传导效应,关系式表明,它们对地幔热力不稳定性都具致稳作用。对于岩石图绝对运动的影响,取决于岩石圈绝对运动方向与地幔所受合力方向的相互关系。     

The study of excitation of the earthquake to Earth's rotation

The earthquake produces a global static displacement field due to the dislocation in the epicenter. This displacement field in turn changes the Earth's inertia tensor, hence exciting the variation of both polar motion and length of day. In general, large earthquake produces greater displacement field, which has greater effects upon the earth rotational properties. In spite of scientists efforts in the last decades, it is found that the polar motion and the length of day excited by earthquake are at least two orders of magnitude less than those derived from observation. In the future with high observational accuracy the effect of earthquake on polar motion and length of day would be observable.Using the fault plane parameters, the location of epicenter and the expression given by Dahlen as well as the step function, the accumulative change of the axial and equatorial moments of inertia of the Earth earthquake occurring in period of 1977–1994 is estimated in this paper. Results have shown that change of pole axis direction induced by single earthquake is independent of the magnitude of the earthquake, which is random, but large earthquake contributes most to the accumulative change of direction of polar drift. The earthquake tends to make the drift of rotational pole towards the direction of 130–150 E. This direction is roughly different to that inferred from observations. Accumulative changes of both the two equatorial principal moments and the axial moment of inertia of the Earth present the strongest non-randomness and secular behaviour. The change depends upon the slip angle of the fault movement in a large extent.     

均匀设计在金属氧化物阳极材料研究中的应用

在金属氧化物阳极材料研究中，采用了均匀设计方法对阳极涂层成分进行优化设计，依据阳极电化学性能试验结果，建立了阳极性能与成分间的数学模型。在回归分析基础上，筛选出金属氧化物阳极涂层成分的最佳配方，并探讨了涂层成分对阳极性能的影响。试验结果表明，贵金属组元铂的加入对金属氧化物阳极的电化学性能影响并不明显；金属氧化物阳极的电化学性能主要受贵金属铱和惰性组元钽的影响。     

海水盐度对铝阳极电化学性能影响的研究

于１９９３年７月－１９９３年９月，利用青岛海滨的新鲜海水配制不同盐度（３０－５）的海水样品。采用ＧＢ４９４８－８５规定的方法研究海水盐度的变化对铝基牺牲性阳极电化学性能的影响。结果表明，海水盐度在３０－１０的范围内变化时对铝阳极的电化学性能无明显影响；当海水盐度降至５后，对阳极的开路电位，闭路电位及电流效率等产生明显影响，使性能指标低于国标要求的范围。     

2003年8月汉中连阴雨过程环流形势分析

本文通过对关铝炭素有限公司预焙阳极工程大气、水、固体废物特征污染物的分析，以及拟建项目环境现状影响预测分析、当地医疗卫生状况调查分析，讨论了该工程建设对人群健康存在的影响，提出了污染物防治、消除或减缓建设项目对居民健康潜在危害的预防措施。     

2-D rotation behavior of a rigid ellipse in confined viscous simple shear: numerical experiments using FEM

The rotation behavior of rigid elliptical inclusions adherent to the viscous matrix in simple shear flow is investigated using a 2-D finite element numerical model. Several simulations were performed using different ratios (S) between shear zone width and inclusion's least principal axis. A computational strategy was devised to calculate pressure and viscous forces exerted on the inclusion and deduce its angular velocity. For large S values, results agree remarkably well with theoretical predictions, while for small S values results deviate significantly from theory but are in agreement with previous analogue experiments. The numerical model provided detailed and coherent information about the physical parameters involved in the process (e.g., pressure, strain rate and vorticity distributions within the model).