共查询到20条相似文献,搜索用时 15 毫秒
1.
The invariant properties of the fundamental system of equations of the mechanics of inhomogeneous fluids and its widely used approximations are analysed by the methods of continuous group theory. Simplifying assumptions significantly alter the invariant properties of the systems of equations. Both extending and contracting the admissible symmetry group can occur and provide evidence of the violation of the conditions of equivalence between the original and derived systems. For example, the use of the incompressibility and Boussinesq approximations leads to extension of the concept of an inertial reference frame to all frames moving relative to one another with arbitrary linear acceleration. 相似文献
2.
We study the nilpotency of the sums of all coefficients of some sorts of products of polynomials over reversible, IFP, and NI rings, and introduce an SCN ring as a generalization. We characterize SCN rings in relation with related ring properties, and also provide several useful properties and ring extensions of SCN rings. 相似文献
3.
A. N. Vetokhin 《Differential Equations》2016,52(3):272-281
We consider parametric families of differential systems with coefficients that are bounded and continuous on the half-line and uniformly in time continuously depend on a real parameter. For each Lyapunov exponent, we construct a family such that the Lyapunov exponent of its systems treated as a function of the parameter is not a lower semicontinuous function for any value of the parameter. 相似文献
4.
5.
We show that many important varieties and sets of varieties of semigroups may be defined by relatively simple and transparent
first-order formulas in the lattice of all semigroup varieties. 相似文献
6.
In this paper, we prove that any subreduct of the class of representable relation algebras whose similarity type includes
intersection, relation composition and converse is a non-finitely axiomatizable quasivariety and that its equational theory
is not finitely based. We show the same result for subreducts of the class of representable cylindric algebras of dimension
at least three whose similarity types include intersection and cylindrifications. A similar result is proved for subreducts
of the class of representable sequential algebras.
Received October 7, 1998; accepted in final form September 10, 1999. 相似文献
7.
We analyze one class of families of integral equations and describe the dependence of the singularities of solutions of integral equations on the dimensions of the families of kernels of equations. On the basis of these results, we propose procedures for the construction of approximate solutions for a small parameter. 相似文献
8.
D. Ya. Khusainov 《Ukrainian Mathematical Journal》1991,43(9):1053-1063
A system of linear functional-differential equations of neutral type is considered. Investigation of stability is carried out by the method of Lyapunov functions of quadratic form. Sufficient conditions for the asymptotic stability and estimates of the exponential decay of solutions for an arbitrary and a small deviation of the argument are obtained.Candidate of the Physicomathematical Sciences.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43. No. 9, pp. 1123–1135, September, 1991. 相似文献
9.
V. Yu. Stolbov 《Journal of Mathematical Sciences》1993,65(5):1868-1873
We state the problem of optimal control of the process of electroplating of parts as a problem of coupled optimization. Problems of optimal control of electroheating and subsequent deformation of a metal billet are studied as a coupled problem. In solving the problems the gradient method and Pontryagin's principle are used.Translated fromMatematicheskie Melody i Fiziko-Mekhanicheskie Polya, Issue 33, 1991, pp. 59–64. 相似文献
10.
Varieties of Sums of Powers describe the additive decompositions of a homogeneous polynomial into powers of linear forms. The study of these varieties dates back to Sylvester and Hilbert, but only few of them, for special degrees and number of variables, are concretely identified. In this paper we aim to understand a general birational behavior of VSP. To do this we birationally embed these varieties into Grassmannians and prove the rational connectedness of many VSP in arbitrary degrees and number of variables. 相似文献
11.
The determination of confidence intervals of deformations was studied for an individual measurement and arithmetical mean common for all points of an experimental family of curves. From the experimental data on the creep of polyamide resin and five different analytical equations of physically nonlinear creep, the problems of the computer approximation of families of creep curves and the determination of the material parameters are discussed. A method is proposed for a quantitative evaluation of the degree of correspondence of the initial data to the similarity of isochronous creep curves and the similarity of the creep curves.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 220–229, March–April, 1976. 相似文献
12.
Din' Zung 《Journal of Mathematical Sciences》1986,35(6):2859-2875
The paper deals with imbedding theorems and harmonic approximation for classes of periodic functions of several variables. Necessary and sufficient conditions for imbedding are found for various classes of smooth functions. The paper contains asymptotic estimates for fractional order derivatives of multidimensional Dirichlet and Favard kernels, for Fourier best approximation and for the Kolmogorov diameter of smooth function classes.Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 10, pp. 207–226, 1984. 相似文献
13.
In this paper we determine the minimum and maximum values of the sum of squares of degrees of bipartite graphs with a given number of vertices and edges. 相似文献
14.
N/Kbe a Galois extension of number fields with finite Galois group G.We describe a new approach for constructing invariants of the G-module structure of the K groups of the ring of integers of N in the Grothendieck group of finitely generated projective Z[G]modules. In various cases we can relate these classes, and their function field counterparts, to the root number class of Fröhlich and Cassou-Noguès. 相似文献
15.
Takemi Yanagimoto David G. Hoel 《Annals of the Institute of Statistical Mathematics》1980,32(1):465-480
Summary Procedures to estimate a dose of which the incidence probability is very small (e.g. 10−6) have been developed to evaluate the safety of chemical compounds. To compare models for estimation of safe doses quantitatively,
a measure of the heaviness of tail of a distribution and a measure of tail at the origin are introduced. These measures have
a theoretical basis for the comparison of tail behavior between distributions. Using the two measures, a tail ordering is
defined to present a criterion for the comparison of models and is discussed for the probit, the logit, the Weibull, the (generalized)
multihit, the (generalized) multitarget and the multistage models.
The multistage model is most conservative among them, while the probit model has the reverse property. The Weibull model is
more conservative than the logit. The multihit and multitarget models are found to be more sensitive than the Weibull and
the logit.
The Institute of Statistical Mathematics National Institute of Environmental Health Sciences 相似文献
16.
Numerical characteristics of identities of associative and non-associative algebras are studied in the paper. It is announced that the sequence of codimensions of an arbitrary associative PI-algebra asymptotically increases and that this is not true in the general non-associative case. 相似文献
17.
R. A. Abusev 《Journal of Mathematical Sciences》1991,56(3):2403-2406
Quadratic errors or unbiased density estimators are obtained for a number of distributions and the cases of normal distribution and Wishart distribution are considered.Translated from Staticheskie Metody Otsenivaniya i Proverki Gipotez, pp. 4–10, 1988. 相似文献
18.
本文分析了15具白骨化尸体标本的股骨汞(Hg),铅(Pb),镉(Cd)元素含量数据,在三年的时间内采集了3次,一共收集到45个数据。首先将这组数据看着纵向数据,利用线性随机效应混合模型、Cox随机混合效应模型进行分析,结果显示,如果对每个白骨化尸体标本建立线性模型,可以精确预测出死亡时间,而且不需要采集铅元素含量数据。混合效应模型的预测效果也很好,最大误差不会超过1个月。其次我们对数据不作任何假设,利用机器学习中随机森林方法分析数据,并利用5折交叉验证方法来判断结果的可靠性,训练集和测试集的NMSE分别为0.1205944,0.5604286,因此可以用训练出的模型来预测死亡时间。 相似文献
19.
A. A. Illarionov 《Mathematical Notes》2011,89(1-2):245-254
We prove an estimate of the number of relative minima of an arbitrary lattice (which can be noninteger and incomplete) located in a given cube. This estimate is correct up to a constant depending on the dimension and rank. 相似文献
20.
V. S. Rykhlov 《Russian Mathematics (Iz VUZ)》2009,53(6):33-43
In spaces of functions square summable on finite intervals we study the simple completeness of the system of eigen- and associated functions for the pencil of ordinary differential operators generated by a differential expression with constant coefficients (we assume that the roots of the corresponding characteristic equation lie on one and the same ray) and specific semisplitting homogeneous boundary value conditions. 相似文献