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71.
Grzegorz ?ysik S?awomir Michalik 《Journal of Mathematical Analysis and Applications》2008,341(1):372-385
We study formal power series solutions to the initial value problem for semilinear heat equation t∂u−Δu=f(u) with polynomial nonlinearity f and prove that they belong to the formal Gevrey class G2. Next we give counterexamples showing that the solution, in general, is not analytic in time at t=0. 相似文献
72.
Olivier Demanze 《Journal of Mathematical Analysis and Applications》2008,338(1):662-674
The point source of this work is Seleznev's theorem which asserts the existence of a power series which satisfies universal approximation properties in C∗. The paper deals with a strengthened version of this result. We establish a double approximation theorem on formal power series using a weighted backward shift operator. Moreover we give strong conditions that guarantee the existence of common universal series of an uncountable family of weighted backward shift with respect to the simultaneous approximation. Finally we obtain results on admissible growth of universal formal power series. We especially prove that you cannot control the defect of analyticity of such a series even if there exist universal series in the well-known intersection of formal Gevrey classes. 相似文献
73.
Karl-Heinz Diener 《Mathematical Logic Quarterly》1993,39(1):492-514
In this paper we generalize the Dedekind theory of order for the natural numbers N to abstract algebras with arbitrarily many finitary or infinitary operations. For any algebra ??, we introduce an algebraic predecessor relation P?? and its transitive hull P*?? coinciding in N with the unary injective successor function' resp. the >-relation. For some important classes of algebras ??, including Peano algebras (absolutely free algebras, word algebras), the algebraic predecessor relation is well-founded. Hence, its transitive hull, the natural ordering >?? of ??, is a well-founded partial order, which turns out to be a convenient device for classifying Peano algebras with respect to the number of operations and their arities. Moreover, the property of well-foundedness is an efficient tool for giving simple proofs of structure theorems as, e. g., that the class of all Peano algebras is closed under subalgebras and non-void direct products. - Finally, we will show how in the case of a formal language ??, i. e., the Peano algebra ?? of expressions (= terms & formulas), relations P??, resp. P*?? can be used to define basic syntactical notions as occurences of free and bound variables etc. without any reference to a particular representation (“coding”) of the formal language. MSC: 03B22, 03E30, 03E75, 03F35, 08A55, 08B20. 相似文献
74.
A short and efficient enyne metathesis route is reported for the construction of a key intermediate required in the synthesis of dysidiolide thus completing its formal synthesis. 相似文献
75.
Cristodor Ionescu 《Rendiconti del Circolo Matematico di Palermo》2009,58(1):45-50
Let u: A → B be a morphism of noetherian local rings. It is known that if u is formally smooth, then Ω
B|A
is formally projective. We give several cases in which the converse is true, in the case of rings containing a field of positive
characteristic.
Work supported by the CEEX program of the Romanian Ministry of Education and Research, Contract 2-CEx06-11-20/2006. 相似文献
76.
August J Weidner 《Fuzzy Sets and Systems》1981,6(1):61-72
A connection between fuzzy sets and Boolean-valued universes is made by developing a formal axiomatic system for fuzzy sets among whose models are suitably interpreted Boolean-valued universes. The formal system is an independent first-order axiomatization of fuzzy set theory which parallels the Zermelo-Fraenkel development of classical set theory. 相似文献
77.
Katsumasa Ishii 《Mathematical Logic Quarterly》2003,49(5):525-535
Two cut‐free sequent calculi which are conservative extensions of Visser's Formal Propositional Logic (FPL) are introduced. These satisfy a kind of subformula property and by this property the interpolation theorem for FPL are proved. These are analogies to Aghaei‐Ardeshir's calculi for Visser's Basic Propositional Logic. 相似文献
78.
In order to provide the theoretical framework necessary to study the neural mechanisms underlying languages, we present here a mathematical formalization of some neural behaviors. In such a context: (i) the neuron is defined as a coupling of automata, dealing with the transduction and codifying processes; (ii) the coupling between neurons is measured by a membership relation defined as the ratio between the transmitted and the system entropies; (iii) the attention given to the messages arriving at the system is considered as the difference between the couplings of the excitatory and inhibitory pools of neurons; (iv) the graphs in the neural systems are described by means of these couplings and, finally (v) the semantic productions are described by the fuzzy formal languages accepted by the automata formalized on these graphs. In such a way, both the verbal and neural semantics can now be correlated and experimentally investigated. 相似文献
79.
80.
为了准确、全面地揭示相机几何指标在立体测绘中的误差传播规律,研究了两线阵CCD相机几何指标差异与定位准确度之间的关系.针对两线阵立体测绘特点,分析了影响测绘定位的几何指标差异参量.在前方空间交会地面点计算公式的基础上,推导并建立了两线阵相机定位准确度模型,据此研究了内方位元素标定误差间的几何指标差异对定位准确度的影响规律.结果表明:主点位置x方向误差间的差异对定位准确度影响显著,当其值从1 μm增至2.5 μm时,定位准确度明显下降了60%,焦距f误差间的差异对定位准确度的影响几乎可忽略.本文所建立的模型与相关研究结论对两线阵CCD相机指标的量化与优化设计具有重要指导意义. 相似文献