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A. González Arias A. del Cueto J. M. Muñoz C. de Francisco L. Torres A. G. Flores M. Zazo J. Iñiguez 《Applied Physics A: Materials Science & Processing》1996,63(5):453-459
Silica may dissolve up to about 0.05 wt% in an iron excess NiZnCo spinel matrix, affecting noticeably the magnetic properties at low and high values of the applied field. The initial permeability is reduced by about 50% with the addition of only 0.1 % SiO2, while the coercivity almost triples, without noticeable changes in porosity or grain distribution. The vacancy and Fe2+ content of the sintered material also show a considerable change. The energy associated to the transformation Fe3+ Fe2+ for the samples without SiO2 was found to be 0.41–0.42 eV, while for the samples with SiO2 additions it decreased to 0.26 eV. The changes in magnetic properties are thought to be caused, more than because of the mentioned changes in ion distribution, by the stresses and defects created in the lattice due to the very small size of the Si4+ ion, which substitutes Fe3+ ions in tetrahedral sites. The transition Fe3+ Fe2+ seems to take place exclusively in the octahedral sites. 相似文献
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We study the derivation of a Langevin equation from a microscopic basis in order to elucidate the nature of the random force. We arrive at the conclusion that the consistent interpretation of the microscopic Langevin equation in terms of a stochastic differential equation (SDE) is according to I
o rules. In addition, the random force is in general not Gaussian, and it is hence not completely characterized by its second moments. 相似文献
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Juan J. Nuño Ballesteros 《Geometriae Dedicata》1993,47(3):241-254
We study the singularities of the tangent developable of a generic curve in 3 and prove that if the curve has no torsion zero points, the number of triple points of that surface must be even. 相似文献
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Victor H. de la Peña 《Journal of Theoretical Probability》1993,6(2):285-302
In this paper we introduce a new tail probability version of Wald's lemma for expectations of randomly stopped sums of independent random variables. We also make a connection between the works of Klass(18, 19) and Gundy(11) on Wald's lemma. In making the connection, we develop new Lenglart and Good Lambda inequalities comparing the tails of various types of adapted processes. As a consequence of our Good Lambda inequalities we include the following result. Let {d i }, {e i } be two sequences of variables adapted to the same increasing sequence of σ-fields ? n ↗?, (e.g., ? n =σ({d i } i=1 n , {E i } i=1 n ), and letN?∞ be a stopping time adapted to {? n }. Then for allp>0, there exists a constant 0<C p <∞ depending onp only, such that $$\mathop {\overline {\lim } }\limits_\lambda \lambda ^p P\left( {\mathop {\sup }\limits_{1 \leqslant n \leqslant N} \left\| {\sum\limits_{i = 1}^n {d_i } } \right\| > \lambda } \right) \leqslant C_p \mathop {\overline {\lim } }\limits_\lambda \lambda ^p P\left( {\mathop {\sup }\limits_{1 \leqslant n \leqslant N} \left\| {\sum\limits_{i = 1}^n {e_i } } \right\| > \lambda } \right)$$ This result holds when the sequences are real, tangent, and either conditionally symmetric or nonnegative, or alternatively, if {d i } is a sequence of independent random variables and {e i } is an independent copy of {d i }, withN a stopping time adapted to the filtration generated by {d i } only. Other examples include Hilbert space valued differentially subordinate conditionally symmetric martingale differences. The result is true for more general operators applied to sequences as shown by an example comparing the square function of a conditionally symmetric sequence to the maximum of its absolute partial sums. 相似文献
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