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871.
Ultrasonic investigations of high-Tc superconductors have been quite successful in determining the magnetic field and temperature dependence of the interaction between magnetic vortices and defect structures in the superconducting state. Recent advances in ultrasonic techniques, allowing the separation of effects due to coupling of the vortex ensemble to modulations of the superconducting current density from those due to pinning, show evidence of reentrant softening of the vortex ensemble as precursor to reentrant melting. It is demonstrated how a related experimental setup can be used to study the magnetic field-induced torque acting on a sample. Torque experiments on highly anisotropic superconductors yield valuable information about the anisotropy of the reduced mass of charge-carriers and the penetration depth. Important advantages of the approach described here over conventional torque experiments are: (a) high sensitivity to small changes in torque even at high ‘bias’-torque; and (b) constant angle between applied magnetic field and sample during the whole experiment, a property that is most important when investigating highly anisotropic superconducting samples in the presence of a magnetic field. Experimental results on a test system show the principle of operation, and investigations of a high-Tc superconducting sample are presented. 相似文献
872.
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874.
The inter-relationship between the orthogonal alignment of polymer helices and improvement of lithium-transport properties of polymer electrolytes has been determined by scanning electron microscopy, differential-scanning calorimetry and dielectric spectroscopy. It is suggested that ordering of the polymer electrolyte accompanied by increased conduction properties is achieved by mutual coordination of local dipole moments of the polar CH2-CH2-O units during casting under a magnetic field. 相似文献
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876.
In today's automotive industry in order to protect car bodies from corrosion, spray or immersion type zinc phosphating processes are applied. In both types, nickel and chromium are widely used though they are harmful to human health and environment. In this study, car body's corrosion performance, coated by no nickel (0 ppm) and low nickel (100, 200, 300 ppm) immersion type zinc phosphating (without chromium passivation) processes, are compared to the bodies that are coated by spray and immersion type processes including nickel (500–700 ppm) and chromium. After analyzing coating weight, composition, morphology of the crystals and salt spray test corrosion performance of car bodies specimens coated by no nickel and low nickel processes are as good as the ones coated by spray and immersion phosphating processes including nickel and chromium. In developing environment consciousness, it is inevitable to favor no nickel or low nickel processes since they give no harm to nature and human health. 相似文献
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878.
Temperature dependences of elastic moduli describing elastic anisotropy in the rage from room temperature to 600 °C are shown. These temperature dependences are in agreement with available values of elastic moduli and temperature coefficients of the elastic moduli at room temperature. They are in agreement with modern quasi-harmonic theory of crystal lattices. Near 285 °C critical changes of effective elastic moduli due to magnetic phase transition are observed. A correlation was made between experimental and theoretical critical changes of longitudinal and transverse elastic wave velocities for different crystallographic directions. It is proved that the critical change of ultrasound wave velocities of this crystal is connected with the single-ion magnetostriction. 相似文献
879.
槽道中方形障碍物绕流的大涡模拟 总被引:6,自引:3,他引:3
本文应用二阶全展开ETG有限元离散格式与大涡模拟相结合的方法对固定在槽道一侧的方形障碍物的绕流进行了数值模拟,计算了雷诺数为40000的湍流情况下的绕流流场,将模拟结果与实验结果及他人的数值结果进行了对比,符合较好,表明大涡模拟与所论的具有较高精度的数值算法相结合,适合于具有大尺度涡的绕流运动流场的分析。 相似文献
880.
Francis Chachula 《Fuel》2003,82(8):929-942
A rutile concentrate recently produced by Lakefield Research Ltd and Syncrude Canada Ltd from athabasca oil sands tailings was characterized and attempts were made to upgrade it to market-grade. The rutile concentrate contained 75.5% TiO2, 18.7% Fe2O3, 1.03% Al2O3, 1.94% SiO2, and 563 ppm Th+U. The amount of rutile (anatase) in the concentrate was estimated to be about 10-17%, and the remaining TiO2 came from ilmenite in various altered forms. Magnetic separation could remove the Fe from the concentrate but it increased the SiO2 content from 1.94 to 6.01%. A reverse flotation process was developed to remove the SiO2. Although the fine dissemination of SiO2 in the rutile matrix limited the removal of SiO2, the upgraded rutile concentrate, containing 87-89% TiO2, could be used as a feedstock to the chloride titanium pigment processes. 相似文献