合金成分对Al-Zn-In-Mg-Ti牺牲阳极性能的影响

利用正交试验的配比方法炼制了不同Zn、In、Mg、Ti含量Al-Zn-In-Mg-Ti牺牲阳极9组,采用恒电流和极化曲线方法评价了牺牲阳极的电化学性能。结果表明:电流效率随着钛含量的增加呈上升趋势,随着铟含量的增加而呈下降趋势,随着锌、镁含量的增加先下降后升高。阳极为均匀溶解,未出现钝化现象,溶解过程表现出2种放电过程。最佳阳极配比(wt%)为:Zn 6.0,In 0.020,Mg 1.5,Ti 0.080,余量为Al。     

大地电磁测深二维反演方法求解复杂电性结构问题的适应性研究

为探讨二维反演方法在三维电性结构中的适应性问题,本研究中设计了一系列的二维/三维正演模型进行实验计算,分析了三维高阻/低阻异常体对模型响应的畸变作用,并从反演模式选择和数据旋转方向两个方面进行模型二维反演的对比分析,与三维反演的结果进行了比较,最后采用了实测数据进一步进行了二维和三维反演的比较实验.实验和研究结果表明,在剖面选择方面,在剖面方向与垂直主构造方向相差不大的情况下,截取剖面方向,将电性主轴旋转到垂直剖面方向的二维反演结果与垂直主构造方向的反演结果都可以较好地还原正演模型,在大的构造的反映上并无太大差异.在地下为二维或近三维条件时,正演模型的主要结构都可以较好地被二维和三维反演解析出来.二维的反演结果可能甚至会比三维的反演结果的边界更清晰,更精确.然而,对于具有较强的三维结构的模型而言,其二维反演结果与原始模型可能仍然存在较大差异,其中TM+TP或TM模式的二维反演结果相对更接近原始模型,而TE模式的结果往往会有较大误差,需要在解释时特别注意以免得出错误结论.     

Exact analytic solutions for the rotation of an axially symmetric rigid body subjected to a constant torque

New exact analytic solutions are introduced for the rotational motion of a rigid body having two equal principal moments of inertia and subjected to an external torque which is constant in magnitude. In particular, the solutions are obtained for the following cases: (1) Torque parallel to the symmetry axis and arbitrary initial angular velocity; (2) Torque perpendicular to the symmetry axis and such that the torque is rotating at a constant rate about the symmetry axis, and arbitrary initial angular velocity; (3) Torque and initial angular velocity perpendicular to the symmetry axis, with the torque being fixed with the body. In addition to the solutions for these three forced cases, an original solution is introduced for the case of torque-free motion, which is simpler than the classical solution as regards its derivation and uses the rotation matrix in order to describe the body orientation. This paper builds upon the recently discovered exact solution for the motion of a rigid body with a spherical ellipsoid of inertia. In particular, by following Hestenes’ theory, the rotational motion of an axially symmetric rigid body is seen at any instant in time as the combination of the motion of a “virtual” spherical body with respect to the inertial frame and the motion of the axially symmetric body with respect to this “virtual” body. The kinematic solutions are presented in terms of the rotation matrix. The newly found exact analytic solutions are valid for any motion time length and rotation amplitude. The present paper adds further elements to the small set of special cases for which an exact solution of the rotational motion of a rigid body exists.     

New paleomagnetic data from Upper Oligocene–Lower Miocene rocks of the Northern Argentine Puna–Southern Bolivian Altiplano: Constraining the age of vertical axis rotations

Along the Central Andes a pattern of vertical axis rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (∼19° S) and clockwise to the south. Different hypothesis and models have been proposed to explain the Central Andean Rotation Pattern (CARP). However, the origin of the CARP is a subject of ongoing debate. Recently, different authors have proposed the possible existence of a close correlation between the time–space distribution of deformation and the amount of registered vertical axis rotations in the Southern Central Andes. In order to further investigate such relationship, new paleomagnetic studies were carried out in Upper Oligocene–Lower Miocene rocks of the Northern Argentine Puna and the Southern Bolivian Altiplano. Our results indicate that while one of the sampled localities did not undergo significant vertical axis rotations, the other two recorded clockwise vertical axis rotations larger than 30°. These results suggest the occurrence of small-block rotations in the Southern Bolivian Altiplano–Northern Argentine Puna prior to 15 Ma, which would correspond to the local accommodation of the regional deformation field.     

不同条件下Cu Pd TiO2多金属纳米电极去除地下水中硝酸盐氮的影响

以Pt为阳极,以Ti纳米管为基底修饰一薄层Pd和Cu构成的多金属纳米电极为阴极,搭建电化学反应器进行去除硝酸盐氮(NO3- N)研究,观察了在不同电流密度、初始浓度和pH值条件下该多金属纳米电极对NO3- N去除率的影响。结果表明,在电流密度为30 mA/cm2,添加050 g/L的 Na2SO4作为支持电解质的条件下,电解90 min后Cu Pd TiO2多金属纳米电极对硝酸盐的去除率可达81%,而相同条件下金属Ti做阴极时对硝酸盐的去除率仅为245%。溶液pH值的改变对 NO3- N的去除效果几乎没有影响;随着电流密度的增高,NO3- N的去除效率也随之提高;而随着溶液初始浓度的升高,NO3- N的去除率反而略有下降。     

ELECTROCHEMICAL BEHAVIOR OF Al-BASIC SACRIFICIAL ANODE AT ESTUARY

The Al-basic sacrificial anode is widely used to protect steel construction from corrosion in seawater,but is not suitable for protecting steel in freshwater. In the estuary area, seawater and freshwater mix anddifferent seawater salinity can be formed in different mixing sites between freshwater and seawater. Basedon the requirements of the Shengli Petroleum Administrative Bureau of China, the effect of seawatersalinity on electrochemical properties of Al-basic anode was studied under laboratory conditions by themethod given in National Standard GB 4948-85 (China Starndard Bureau, 1985). No obvious effectwas found when seawater salinity was 30 to 10, but obvious effect on anodic open circuit potential, closedcircuit potential and current efficiency was found when seawater salinity was 5. These values are lowerthan those given in the Naional Standard.     

陕西临潼骊山地区的地质构造演化

本文依据最新资料对骊山地区太华群地层进行划分对比,并且从变形、变质等方面,应用板块构造、韧性剪切断裂等理论对骊山构造演化进行了论述。     

Record of deformation by secondary magnetic remanences and magnetic anisotropy in the Nar/Phu valley (central Himalaya)

Secondary magnetic remanences residing in pyrrhotite and anisotropy of magnetic susceptibility (AMS) were studied in low-grade metamorphic carbonates of the Tethyan Himalaya in Nar/Phu valley (central Nepal) and used for interpretation of tectonic deformations. The characteristic remanence (ChRM) is likely of thermomagnetic origin related to post-peak metamorphic cooling occurring after the Eohimalayan phase (35–32 Ma). The ChRM postdates small-scale folding (main Himalayan folding F1 and F2) as shown by a negative fold test of site mean directions at 99% confidence level, and has been probably acquired between 32 and 25 Ma. Late-orogenic long-wavelength folding associated with the Chako antiform (CA) is recorded by the spatial dispersion of ChRM directions and the distribution of the main axes of the AMS tensor. The mean tilting of the ChRM direction since remanence acquisition (≈20–30°) approximately coincides with the tilting of the CA (31°) at the study area indicating that the pyrrhotite remanence predates the CA (CA formed at <18 Ma according to preliminary U/Pb dating). However, comparison of tilt angles of remanence directions and AMS tensor axes suggests that remanence acquisition was not completed before the onset of the CA formation. This could imply a younger age (Early Miocene or even younger) of the ChRM. Using the distribution of remanence directions along a small-circle as well as the distribution of AMS tensor axes, a clockwise mean rotation of 16° is obtained for a remanence age of ≈30 Ma. An Early Miocene remanence age would not change this result substantially. Compilation of rotations in the Tethyan Himalaya deduced from secondary pyrrhotite remanences reveals an increasing clockwise rotation from the Hidden valley in the W to the Shiar valley in the E (≈150 km distance), incompatible with an oroclinal bending model.     

On the Effect of Planetary Rotation on Shear and Density Layers in Stratified Flows

The effect of the Coriolis forces on the dynamicsof shear and density layers instratified flows is investigated, an effectthat has not been taken into account inmost previous studies of turbulence-meanfield or wave-mean field interactions.For instance, recent studies have shownthat shear and density layers can grow inthe presence of turbulence in a stronglystratified fluid but the effect of planetaryrotation was not taken into account. Toaddress this problem, wave-mean flowinteraction in a stratified fluid is hereinvestigated in the presence of rotation usingdirect numerical simulation. The results showthat the wave-mean flow interactionand the formation of layers is less intensewhen rotation is present because thehorizontal mean motions are deviated by theCoriolis forces, which tends to reducethe distortion of the wave field, and thusthe wave-induced fluxes of buoyancy andmomentum. This effect appears even when therotation rate is weak.     

Prediction of Earth orientation parameters by artificial neural networks

 Earth orientation parameters (EOPs) [polar motion and length of day (LOD), or UT1–UTC] were predicted by artificial neural networks. EOP series from various sources, e.g. the C04 series from the International Earth Rotation Service and the re-analysis optical astrometry series based on the HIPPARCOS frame, served for training the neural network for both short-term and long-term predictions. At first, all effects which can be described by functional models, e.g. effects of the solid Earth tides and the ocean tides or seasonal atmospheric variations of the EOPs, were removed. Only the differences between the modeled and the observed EOPs, i.e. the quasi-periodic and irregular variations, were used for training and prediction. The Stuttgart neural network simulator, which is a very powerful software tool developed at the University of Stuttgart, was applied to construct and to validate different types of neural networks in order to find the optimal topology of the net, the most economical learning algorithm and the best procedure to feed the net with data patterns. The results of the prediction were analyzed and compared with those obtained by other methods. The accuracy of the prediction is equal to or even better than that by other prediction methods. Received: 6 February 2001 / Accepted: 23 October 2001