A self-designed test and the elliptical ring test were applied to test the early autogenous shrinkage and crack resistance of fly ash high-strength lightweight aggregate concrete in which 10-30% of cement was replaced by equivalent amounts of fly ash of different fineness. Test data of reference lightweight aggregate concrete were provided. The results showed that (a) the early autogenous shrinkage of concrete was restrained in fly ash highstrength lightweight aggregate concrete, and further analysis indicated higher fly ash content and higher fly ash fineness resulted in less autogenous shrinkage; (b) in a lower water-binder ratio, early autogenous shrinkage increased significantly as the water-binder ratio decreased, and, moreover, pre-wetting of lightweight aggregate had a great effect on controlling early autogenous shrinkage; (c) the elliptical ring test results indicated that the addition of fly ash significantly improved crack resistance of lightweight aggregate concrete and that this improvement becomes obvious with increasing fineness of fly ash. Therefore, in practice, the addition of fly ash could be a technical alternative to reduce early autogenous shrinkage and to enhance the crack resistance of lightweight aggregate concrete.
Ferroelectric cathodes exhibit huge potentials in high-power microwave tube electron beam source, panel display, and the propeller space navigation, due to their superior properties. The material properties of the ferroelectric cathode have been proved to have a significant influence on electron emission, which is indicated in recent research work. In the course of electron emission, the variation of polarization can be caused by non-shielded surface charge which is induced by high trigger voltage. A certain relationship may be found between polarization variation and current intensity of electron emission. To study the relationship between current intensity of electron emission and polarization variation in ferroelectric cathodes, the samples of lanthanum-doped lead zirconate stannate titanate ferroelectric and antiferroelectric ceramics are prepared by the method of solid state calcinations, and the polarization variations of the material under different voltages are measured in the positive half cycle test of hysteresis loop. The curve of the electron emission current intensity versus the trigger voltage is measured, and then the relationship between electron emission current intensity and polarization variation is investigated. The results show that the electron emission current intensities of the two samples are both directly proportional to the polarization variation.
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