The aim of this paper is to elaborate the power of cooperation in generating and analysing (handwritten) characters by array grammars. We present various non-context-free sets of arrays that can be generated in a simple way by cooperating distributed array grammar systems with prescribed teams working in diierent modes and show the power of the mechanism of cooperation for picture description a...

We introduce and characterize angular right symmetric approximate points of the algebra all bounded linear operators defined on either real or complex Hilbert spaces.

An uncountable collection of uniformly arcwise connected plane Suslinian dendroids is constructed which shows that the negations of the following properties: local connectedness, smoothness, pointwise smoothness, hereditary contractibility, and selectibility are not countable in this class of

Let V be a Hilbert space, a(·, ·) : V × V → lR a bounded, V-elliptic bilinear form and : V → lR a bounded linear functional. We want to approximate the variational equation: Find u ∈ V such that (3.1) a(u, v) = (v) , v ∈ V. We recall that the Lax-Milgram Lemma ensures the existence and uniqueness of a solution of (3.1). Now, given a finite-dimensional subspace V h ⊂ V , dim V h = n h , the Ritz...

Some versions of the maximum common subgraph problem are studied and approximation algorithms are given. The maximum bounded common induced subgraph problem is shown to be Max SNP-hard and the maximum unbounded common induced subgraph problem is shown to be as hard to approximate as the maximum independent set problem. The maximum common induced connected subgraph problem is still harder to app...

Approximate solutions for optimization problems become of interest if the ‘true’ optimum cannot be found: this may happen for the simple reason that an optimum does not exist or because of the ‘bounded rationality’ (or bounded accuracy) of the optimizer. This paper characterizes several approximate solutions by means of consistency and additional requirements. In particular we consider invarian...