Axiomatizations of quasi-Lovász extensions of pseudo-Boolean functions

We introduce the concept of quasi-Lovász extension as being a mapping \({f\colon I^n\to\mathbb{R}}\) defined on a nonempty real interval I containing the origin and which can be factorized as f(x ₁, . . . , x _n ) =  L(φ(x ₁), . . . , φ(x _n )), where L is the Lovász extension of a pseudo-Boolean function \({\psi\colon \{0, 1\}^n \to \mathbb{R}}\) (i.e., the function \({L\colon \mathbb{R}^n \to \mathbb{R}}\) whose restriction to each simplex of the standard triangulation of [0, 1] ⁿ is the unique affine function which agrees with ψ at the vertices of this simplex) and \({\varphi\colon I \to \mathbb{R}}\) is a nondecreasing function vanishing at the origin. These functions appear naturally within the scope of decision making under uncertainty since they subsume overall preference functionals associated with discrete Choquet integrals whose variables are transformed by a given utility function. To axiomatize the class of quasi-Lovász extensions, we propose generalizations of properties used to characterize Lovász extensions, including a comonotonic version of modularity and a natural relaxation of homogeneity. A variant of the latter property enables us to axiomatize also the class of symmetric quasi-Lovász extensions, which are compositions of symmetric Lovász extensions with 1-place nondecreasing odd functions.     

Asymptotic modelling of a Signorini problem of generalized Marguerre-von Kármán shallow shells

Chacha and Bensayah [Asymptotic modeling of a Coulomb frictional Signorini problem for the von Kármán plates, C. R. Mécanique 336 (2008), pp. 846–850] have studied the asymptotic modelling of Coulomb frictional unilateral contact problem between an elastic nonlinear von Kármán plate and a rigid obstacle. The main result obtained is that the leading term of the asymptotic expansion is characterized by a two-dimensional Signorini problem but without friction. In this article, we extend this study to the case of a shallow shell under generalized Marguerre-von Kármán conditions.     

Application of Topological Degree to the Study of Bifurcation in von Kármán Equations

The aim of this paper is to illustrate the use of topological degree for the study of bifurcation in von Kármán equations with two real positive parameters and for a thin elastic disk lying on the elastic base under the action of a compressing force, which may be written in the form of an operator equation F(x, , ) = 0 in some real Banach spaces X and Y. The bifurcation problem that we study is a mathematical model for a certain physical phenomenon and it is very important in the mechanics of elastic constructions. We reduce the bifurcation problem in the solution set of equation F(x, , ) = 0 at a point (0, ₀, ₀) X × IR ₊ ² to the bifurcation problem in the solution set of a certain equation in IR ⁿ at a point (0, ₀, ₀) IR ⁿ × IR ₊ ², where n = dim Ker F _x (0, ₀, ₀) and F _x (0, ₀, ₀): X Y is a Fréchet derivative of F with respect to x at (0, ₀, ₀). To solve the bifurcation problem obtained as a result of reduction, we apply homotopy and degree theory.     

Explicit evaluations of Turán expressions

Summary Positive representations for [P _n ^(λ) (x)]²−P _n ^−1/(λ) (x)P _n ^+1/(λ) (x) and for analogous expressions involving orthogonal polynomials are obtained. This is an excerpt from the author's doctoral dissertation, written under the direction of ProfessorW. Seidel, to whom the author is grateful for his encouragement and assistance.     

On a conjecture of Károly Bezdek and János Pach

Summary The following conjecture of K\'aroly Bezdek and J\'anos Pach is cited in~[1]. If <InlineEquation ID=IE"1"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"2"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"3"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"4"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"5"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"6"><EquationSource Format="TEX"><![CDATA[$]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>K\subset{\mathbb R}^d$ is a convex body then any packing of pairwise touching positive homothets of $K$ consists of at most $2^d$ copies of $K$. We prove a weaker bound, $2^{d+1}$.     

Convergence of the q Analogue of Szász-Beta-Stancu Operators

In the present paper, we propose the q analogue of Sz a′sz-Beta-Stancu operators. By estimate the moments, we establish direct results in terms of the modulus of smoothness. Investigate the rate of point-wise convergence and weighted approximation properties of the q operators. Voronovskaja type theorem is also obtained.Our results generalize and supplement some convergence results of the q-Sz a′sz-Beta operators, thus they improve the existing results.     

The rank reduction procedure of Egerváry

Here we give a survey of results concerning the rank reduction algorithm developed by Egerváry between 1953 and 1958 in a sequence of papers.     

A new construction of Szász-Mirakyan operators

The paper aims to study a generalization of Szász-Mirakyan-type operators such that their construction depends on a function ρ by using two sequences of functions. To show how the function ρ play a crucial role in the design of the operator, we reconstruct the mentioned operators which preserve exactly two test functions from the set \(\left \{ 1,\rho ,\rho ^{2}\right \}\). We show that these operators provide weighted uniform approximation over unbounded interval. We establish the degree of approximation in terms of a weighted moduli of smoothness associated with the function ρ. Also a Voronovskaya type result is presented. Finally some graphical examples of the mentioned operators are given. Our results show that mentioned operators are sensitive or flexible to point of wive of the rate of convergence to f, depending on our selection of ρ.     

Asymptotic solution of a turán-type problem

LetA, B, C be disjointk-element sets. It is shown that if a 2k-graph onn vertices contains no three edges of the formA B, A C, B C then it has at most edges. Moreover, this is essentially best possible.     

Notes on a problem of Turán

Let z1,z2, ... ,znbe complex numbers, and write S= z ^j _{1 + ... +} z ^j _n for their power sums. Let R _n= min_{z 1,z2,...,zn} max_1&le;j&le;n &verbar;Sj&verbar; where the minimum is taken under the condition that max_1&le;t&le;n &verbar;z_t&verbar; = 1 Improving a result of Komlós, Sárközy and Szemerédi (see [KSSz]) we prove here that Rn &lt;1 -(1 - ") log log n /log n We also discuss a related extremal problem which occurred naturally in our earlier proof ([B1]) of the fact that Rn &gt;&half;     

A note on the Structure of Turán Densities of Hypergraphs

Let r ≥ 2 be an integer. A real number α ∈ [0, 1) is a jump for r if there exists c > 0 such that no number in (α, α + c) can be the Turán density of a family of r-uniform graphs. A result of Erd?s and Stone implies that every α ∈ [0, 1) is a jump for r = 2. Erd?s asked whether the same is true for r ≥ 3. Frankl and Rödl gave a negative answer by showing an infinite sequence of non-jumps for every r ≥ 3. However, there are still a lot of open questions on determining whether or not a number is a jump for r ≥ 3. In this paper, we first find an infinite sequence of non-jumps for r = 4, then extend one of them to every r ≥ 4. Our approach is based on the techniques developed by Frankl and Rödl.     

Global stabilization of a dynamic von Kármán plate with nonlinear boundary feedback

We consider a fully nonlinear von Kármán system with, in addition to the nonlinearity which appears in the equation, nonlinear feedback controls acting through the boundary as moments and torques. Under the assumptions that the nonlinear controls are continuous, monotone, and satisfy appropriate growth conditions (however, no growth conditions are imposed at the origin), uniform decay rates for the solution are established. In this fully nonlinear case, we do not have, in general, smooth solutions even if the initial data are assumed to be very regular. However, rigorous derivation of the estimates needed to solve the stabilization problem requires a certain amount of regularity of the solutions which is not guaranteed. To deal with this problem, we introduce a regularization/approximation procedure which leads to an approximating problem for which partial differential equation calculus can be rigorously justified. Passage to the limit on the approximation reconstructs the estimates needed for the original nonlinear problem.The material of M. A. Horn is based upon work partially supported under a National Science Foundation Mathematical Sciences Postdoctoral Research Fellowship. I. Lasiecka was partially supported by National Science Foundation Grant NSF DMS-9204338.     

Instabilities and bifurcations of von Kármán similarity solutions in swirling viscoelastic flow

We derive an asymptotic model that describes the swirling flow of a viscoelastic fluid between a rotating cone and a stationary plate when the gap angle, , is small and inertia is neglected. The model, which uses the Phan-Thien Tanner (PTT) constitutive law, is valid in the limit a 0 and for Deborah number, De, order unity. We show that the model admits similarity solutions of von Kármán type. A solution corresponding to a viscometric flow is obtained. This base flow, which exhibits shear thinning if the PTT parameter 0, is linearly stable if the Deborah number De is less than a critical value De _c and unstable if De > De _c . The critical Deborah number is a decreasing function of the retardation parameter , and an increasing function of . The method of Lyapunov-Schmidt is used to determine the nature of bifurcation when De is close to De _c . Our analysis shows that there is a supercritical pitchfork bifurcation at De=De _c .     

On a class of Szász-Mirakyan type operators

The actual construction of the Szász-Mirakyan operators and its various modifications require estimations of infinite series which in a certain sense restrict their usefulness from the computational point of view. Thus the question arises whether the Szász-Mirakyan operators and their generalizations cannot be replaced by a finite sum. In connection with this question we propose a new family of linear positive operators.     

Pointwise characterization for combinations of Szász-Mirakjan operators

The purpose of this paper is to characterize the pointwise rate of convergence for the combinations of Szász-Mirakjan operators using Ditzian-Totik modulus of smoothness.     

S-orthogonality and construction of Gauss-Turán-type quadrature formulae

Using the theory of s-orthogonality and reinterpreting it in terms of the standard orthogonal polynomials on the real line, we develop a method for constructing Gauss-Turán-type quadrature formulae. The determination of nodes and weights is very stable. For finding all weights, our method uses an upper triangular system of linear equations for the weights associated with each node. Numerical examples are included.