Characterization of integral operators with semi-separable kernels with symmetries

We characterize integral operators with semi-separable kernels in a certain class that have different symmetries. We treat the selfadjoint case, the positive case, the J-unitary case, the positive real case, the dissipative case and the contractive case.     

传统粉笔字教学与多媒体教学的影响分析

多媒体技术进入大学课堂推动了教学的改革,也引发了人们的进一步思考:传统粉笔字教学和多媒体教学从哪些方面影响着教学过程和教学质量?本文通过抽样调查,获取有关数据资料,运用因子分析方法对调查数据进行分析,寻找影响教学的因子,然后利用方差分析检验各因素的显著性,最后利用Logistic回归分析方法建立教学方式选择模型,进一步分析影响教学的各因素,为教学方式的选择提供了理论依据。     

On Choosability with Separation of Planar Graphs with Forbidden Cycles

We study choosability with separation which is a constrained version of list coloring of graphs. A ‐list assignment L of a graph G is a function that assigns to each vertex v a list of at least k colors and for any adjacent pair , the lists and share at most d colors. A graph G is ‐choosable if there exists an L‐coloring of G for every ‐list assignment L. This concept is also known as choosability with separation. We prove that planar graphs without 4‐cycles are (3, 1)‐choosable and that planar graphs without 5‐ and 6‐cycles are (3, 1)‐choosable. In addition, we give an alternative and slightly stronger proof that triangle‐free planar graphs are (3, 1)‐choosable.     

Structure of digraphs associated with quadratic congruences with composite moduli

We assign to each positive integer n a digraph G(n) whose set of vertices is H={0,1,…,n-1} and for which there exists a directed edge from a∈H to b∈H if . Associated with G(n) are two disjoint subdigraphs: G₁(n) and G₂(n) whose union is G(n). The vertices of G₁(n) correspond to those residues which are relatively prime to n. The structure of G₁(n) is well understood. In this paper, we investigate in detail the structure of G₂(n).     

On the construction of the Lyapunov function with sign-definite derivative with the help of auxiliary functions with sign-constant derivatives

The short survey of studies of the asymptotic stability with the help of auxiliary functions (positive definite and nonnegative) whose derivatives are nonpositive by virtue of the equations of perturbed motion and the construction of positive definite Lyapunov functions with negative definite derivatives on the basis of these auxiliary functions is given. The example of the construction of the Lyapunov function with the use of an auxiliary nonnegative function with nonpositive derivative is presented.     

Diagnosis of dyslexia with low quality data with genetic fuzzy systems

For diagnosing dyslexia in early childhood, children have to solve non-writing based graphical tests. Human experts score these tests, and decide whether the children require further consideration on the basis of their marks.Applying artificial intelligence techniques for automating this scoring is a complex task with multiple sources of uncertainty. On the one hand, there are conflicts, as different experts can assign different scores to the same set of answers. On the other hand, sometimes the experts are not completely confident with their decisions and doubt between different scores. The problem is aggravated because certain symptoms are compatible with more than one disorder. In case of doubt, the experts assign an interval-valued score to the test and ask for further information about the child before diagnosing him.Having said that, exploiting the information in uncertain datasets has been recently acknowledged as a new challenge in genetic fuzzy systems. In this paper we propose using a genetic cooperative-competitive algorithm for designing a linguistically understandable, rule-based classifier that can tackle this problem. This algorithm is part of a web-based, automated pre-screening application that can be used by the parents for detecting those symptoms that advise taking the children to a psychologist for an individual examination.     

Simulation of flows with strong shocks with an adaptive conservative scheme

In the present work, numerical simulations of unsteady flows with moving shocks are presented. An unsteady mesh adaptation method, based on error equidistribution criteria, is adopted to capture the most important flow features. The modifications to the topology of the grid are locally interpreted in terms of continuous deformation of the finite volumes built around the nodes. The arbitrary Lagrangian–Eulerian formulation of the Euler equations is then applied to compute the flow variable over the new grid without resorting to any explicit interpolation step. The numerical results show an increase in the accuracy of the solution, together with a strong reduction of the computational costs, with respect to computations with a uniform grid using a larger number of nodes.     

帕金森病患者左旋多巴治疗时测定血同型半胱氨酸水平的临床意义

目的探讨接受左旋多巴治疗的帕金森病（PD）患者血同型半胱氨酸水平与临床特征的关系及测定的意义。方法测定44例PD患者（PD组）与38例健康体检者（对照组）的血同型半胱氨酸、叶酸、维生素B12水平并进行比较,将PD组分为≥14mmol/L与＜14mmol/L两个亚组,比较两组统一帕金森量表评分。分析PD患者血同型半胱氨酸水平的影响因素。结果 PD组患者血同型半胱氨酸水平[（16.1±7.8）μmol/L]高于对照组[（10.9±2.8）μmol/L],高同型半胱氨酸水平与叶酸、维生素B12水平呈负相关（r=-0.467,P＜0.01;r=-0.347,P＜0.05）,与左旋多巴用量及UPDRSⅢ呈正相关（r=0.464,P＜0.01;r=0.378,P＜0.05）,与年龄、起病年龄、病程、左旋多巴使用时间无关（均P＞0.05）,≥14mmol/L与＜14mmol/L两组UPDRS评分的差异无统计学意义（P＞0.05）。结论左旋多巴治疗会导致高同型半胱氨酸血症发生,补充叶酸及维生素B12治疗可能是有效的治疗方法。     

Equalities of ideals associated with two projections in rings with involution

In this article we study various right ideals associated with two projections (self-adjoint idempotents) in a ring with involution. Results of O.M. Baksalary, G. Trenkler, R. Piziak, P.L. Odell and R. Hahn about orthogonal projectors (complex matrices which are Hermitian and idempotent) are considered in the setting of rings with involution. New proofs based on algebraic arguments, rather than finite-dimensional and rank theory, are given.     

Extremes of Markov-additive Processes with One-sided Jumps, with Queueing Applications

Through Laplace transforms, we study the extremes of a continuous-time Markov-additive process with one-sided jumps and a finite-state background Markovian state-space, jointly with the epoch at which the extreme is ‘attained’. For this, we investigate discrete-time Markov-additive processes and use an embedding to relate these to the continuous-time setting. The resulting Laplace transforms are given in terms of two matrices, which can be determined either through solving a nonlinear matrix equation or through a spectral method. Our results on extremes are first applied to determine the steady-state buffer-content distribution of several single-station queueing systems. We show that our framework comprises many models dealt with earlier, but, importantly, it also enables us to derive various new results. At the same time, our setup offers interesting insights into the connections between the approaches developed so far, including matrix-analytic techniques, martingale methods, the rate-conservation approach, and the occupation-measure method. We also study networks of fluid queues, and show how the results on single queues can be used to find the Laplace transform of the steady-state buffer-content vector; it has a matrix quasi-product form. Fluid-driven priority systems also have this property.     

Groups with an element permuting with finitely many of its conjugates

We study the problem as to which is the cardinality of connected components of the graph Γ_α, defined as follows. Let G be a group and a an element of G. The vertex set V(Γ_α) of the graph is the conjugacy class of elements,Cl _G(a), and two vertices x and y of the graph Γ_α are bridged by an edge iff x=y. If the intersectionC _G(a)∩Cl _G(a) is finite, Γ_α is locally finite. We prove that connected components of the locally finite graph Γ_α are finite in some classes of groups. Supported by RFFR grant No. 94-01-01084. Translated fromAlgebra i Logika, Vol. 35, No. 5, pp. 543–551, September–October, 1996.     

Stability of Linear Integrodifferential Systems with Time-varied Confficients with Large Scale

51.IntroductionConsideralinearintegrodifferentialsystemswithtime-variedconfficientswherex6R",A(t)isanXnrealmatrixfunctioncontinuousforoO.ManyscholarshavecontributedtheirpaPers[1-4]todiscussstabilityofzerosolutionofsystem(1.l).Inthispaper,weassumethatsystem(1.1)canbedecomPOsedintotheform=n,A,j(t)isaniXnjrealmatrixfunctioncontinuousforo相似文献