Some results on extending and sharpening the Weierstrass product inequalities

In this paper, we establish two extensions of Weierstrass's inequality involving symmetric functions by means of the theory of majorization, and give an interesting sharpness of Weierstrass's inequality by using the arithmetic-geometric mean inequality. Furthermore, we apply these results to improve a well-known inequality and deduce some new inequalities.     

An overview of some recent results on the Euler system of isentropic gas dynamics

This overview is concerned with the well-posedness problem for the isentropic compressible Euler equations of gas dynamics. The results we present are in line with the programof investigatingthe efficiency of different selection criteria proposed in the literature in order to weed out non-physical solutions to more-dimensional systems of conservation laws and they build upon the method of convex integration developed by De Lellis and Székelyhidi for the incompressible Euler equations. Mainly following [5], we investigate the role of the maximal dissipation criterion proposed by Dafermos in [6]: we prove how, for specific pressure laws, some non-standard (i.e. constructed via convex integration methods) solutions to the Riemann problem for the isentropic Euler system in two space dimensions have greater energy dissipation rate than the classical self-similar solution emanating from the same Riemann data. We therefore show that the maximal dissipation criterion proposed by Dafermos does not favour in general the self-similar solutions.     

The nonsymmetric case of the Keller-Segel model in chemotaxis: some recent results

Looking at the nonsymmetric case of a reaction-diffusion model known as the Keller-Segel model, we summarize known facts concerning (global in time) existence and prove new blowup results for solutions of this system of two strongly coupled parabolic partial differential equations. We show in Section 4, Theorem 4, that if the solution blows up under a condition on the initial data, blowup takes place at the boundary of a smooth domain . Using variational techniques we prove in Section 5 the existence of nontrivial stationary solutions in a special case of the system. Received April 2000     

Some recent and new results on the maximum entropy distribution

This letter concerns the maximum entropy (ME) distribution proposed by Theil and Laitinen (1980); it summarizes some of the results obtained with this distribution and its explores the conditioning of the ME covariance matrix as the number of variables increases.     

A short proof of some recent results related to Cesàro function spaces

We give a short proof of the recent results that, for every 1≤p<∞$1\le p<\infty$, the Cesàro function space Ce_sp(I)$Ce{s}_p\left(I\right)$ is not a dual space, has the weak Banach–Saks property and does not have the Radon–Nikodym property.     

Remarks on some recent metrical common fixed point theorems

In an interesting article, Bouhadjera and Godet-Thobie (2009) [6] introduced notions of subcompatibility and subsequential continuity, and utilized them to prove several common fixed point theorems. The results of the aforementioned article contain flaws, and they are not correct in their present form. But these results can be recovered in two ways by strengthening either of the newly introduced definitions. The results, in their corrected form, still bring about noted improvements over a multitude of relevant fixed point theorems of the existing literature, substantiating the utility of these (two) new notions.     

Comments on some recent methods for the simultaneous determination of polynomial zeros

In this note we give some comments on the recent results concerning a simultaneous method of the fourth-order for finding complex zeros in circular interval arithmetic. The main discussion is directed to a rediscovered iterative formula and its modification, presented recently in (Sun and Kosmol (J. Comput. Appl. Math. 130 (2001) 293)). The presented comments include some critical parts of the papers (Jpn. J. Indust. Appl. Math. 15 (1998) 295) and (Sun and Kosmol, 2001) which treat the same subject.     

关于单叶函数中几个结果的注记

首先就Mbius变换在几何函数论上应用时存在的两个误区予以讨论,指出其存在的问题与如何改正;其次明确地指出用Baernstein方法估计m次对称单叶函数之逆函数系数时的不足之处;最后就S ingh与Puri一文中的一个结果给以改正,并用Ruschew eyh的共轭方法得到该结果成立的最佳范围.     

A survey of recent results on congruence lattices of lattices

We review recent results on congruence lattices of (infinite) lattices. We discuss results obtained with box products, as well as categorical, ring-theoretical, and topological results. Received March 13, 2002; accepted in final form September 24, 2002. RID="h1" ID="h1"     

Some recent results on drazin monotonicty of property n martices

If a square matrix has a nonnegarive power it is called a property-n matrix. In a recent paper [12] Werner derived some interesting necessary and sufficient conditions for a property n property-n matrix to be Drazin-montone. In particular, it was shown that a property -n matrix with ind(A) = k is Drazin-monotone if and only if A^2k+1 is weak-r-monotone. Our principal aim here is to show how this result can he strengthened considerably. To tackle this problem we also present several further results on the structure of Drazin-monotone (property-n) matrices.     

A survey of recent results on continuous-time Markov decision processes

This paper is a survey of recent results on continuous-time Markov decision processes (MDPs) withunbounded transition rates, and reward rates that may beunbounded from above and from below. These results pertain to discounted and average reward optimality criteria, which are the most commonly used criteria, and also to more selective concepts, such as bias optimality and sensitive discount criteria. For concreteness, we consider only MDPs with a countable state space, but we indicate how the results can be extended to more general MDPs or to Markov games. Research partially supported by grants NSFC, DRFP and NCET. Research partially supported by CONACyT (Mexico) Grant 45693-F.     

Additional results on the series expansions of some trigonometric and hyperbolic functions

We establish some recurrence relations for the successive derivates atx=0 of some trigonometric and hyperbolic functions. We also construct an arithmetical triangle which gives immediately, by recurrence, the derivatives of the desidered order, of the functions sec, tan, cosec, cot, sech and tanh.     

The analysis of the number of fixed points in the key extending algorithm of RC4

The probabilities of the state transitions of the initial value So in the S table of RC4 are described by a kind of bistochastic matrices, and then a computational formula for such bistochastic matrices is given, by which the mathematical expectation of the number of fixed points in the key extending algorithm of RC4 is obtained. As a result, a statistical weakness of the key extending algorithm of RC4 is presented.