Yanqiu Wang

In the present work, the microstructure of the melt-spun Al 90 Ce 10 alloy has been characterized using X-ray diffraction and transmission electron microscopy together with energy-dispersive spectrometry. It has been found that the microstructure of the melt-spun Al 90 Ce 10 alloy is composed of the amorphous phase, f -Al, f -Al 11 Ce 3 , Al 3 Ce and unidentified phases, quite different from that of the ingot-like alloy consisting of coarse primary f -Al- f -Al 11 Ce 3 dendrites embedded in the f -Al- f -Al 11 Ce 3 eutectic matrix. Moreover, the amorphous phase is dominant in the melt-spun Al 90 Ce 10 alloy according to the XRD and TEM results. Al 3 Ce particles, less than 100 nm in size, are dispersed in the partial amorphous phase. Polygonal f -Al 11 Ce 3 crystals embedded in the f -Al matrix are also observed. The presence of the hexagonal, kite-like and petal-like intermetallic particles surrounded by the amorphous phase indicates that there exist micro-inhomogeneous structures in the Al 90 Ce 10 melt. These results demonstrate that the overheating of the melt has a significant effect on the amorphization of the Al 90 Ce 10 alloy

Let ≤r and ≤sbe two binary relations on 2ℕ which are meant as reducibilities. Let both relations be closed under finite variation and consider the uniform distribution on 2ℕ, which is obtained by choosing elements of 2ℕ by independent tosses of a fair coin.Then we might ask for the probability that the lower ≤r-cone of a randomly chosen set X, that is, the class of all sets A with A ≤rX, differs from the lower ≤s-cone of X. By c osure under finite variation, the Kolmogorov 0-1 aw yields immediately that this probability is either 0 or 1; in case it is 1, the relations are said to be separable by random oracles.Again by closure under finite variation, for every given set A, the probability that a randomly chosen set X is in the upper ≤r-cone of A is either 0 or 1; let Almostr be the class of sets for which the upper ≤r-cone has measure 1. In the following, results about separations by random oracles and about Almost classes are obtained in the context of generalized reducibilities, that is, for binary relations on 2ℕ which can be defined by a countable set of total continuous functionals on 2ℕ in the same way as the usual resource-bounded reducibilities are defined by an enumeration of appropriate oracle Turing machines. The concept of generalized reducibility comprises a natura resource-bounded reducibilities, but is more general; in particular, it does not involve any kind of specific machine model or even effectivity. The results on generalized reducibilities yield corollaries about specific resource-bounded reducibilities, including several results which have been shown previously in the setting of time or space bounded Turing machine computations