Semigroups Arising From Asynchronous Automata

We introduce a new class of semigroups arising from a restricted class of asynchronous automata. We call these semigroups "expanding automaton semigroups." We show that the class of synchronous automaton semigroups is strictly contained in the class of expanding automaton semigroups, and that the class of expanding automaton semigroups is strictly contained in the class of asynchronous automaton semigroups. We investigate the dynamics of expanding automaton semigroups acting on regular rooted trees, and show that undecidability arises in these actions. We show that this class is not closed under taking normal ideal extensions, but the class of asynchronous automaton semigroups is closed under taking these extensions. We construct every free partially commutative monoid as a synchronous automaton semigroup.Comment: 31 pages, 4 figure

Mace4 Reference Manual and Guide

Mace4 is a program that searches for finite models of first-order formulas. For a given domain size, all instances of the formulas over the domain are constructed. The result is a set of ground clauses with equality. Then, a decision procedure based on ground equational rewriting is applied. If satisfiability is detected, one or more models are printed. Mace4 is a useful complement to first-order theorem provers, with the prover searching for proofs and Mace4 looking for countermodels, and it is useful for work on finite algebras. Mace4 performs better on equational problems than did our previous model-searching program Mace2.Comment: 17 page

MACE 2.0 Reference Manual and Guide

MACE is a program that searches for finite models of first-order statements. The statement to be modeled is first translated to clauses, then to relational clauses; finally for the given domain size, the ground instances are constructed. A Davis-Putnam-Loveland-Logeman procedure decides the propositional problem, and any models found are translated to first-order models. MACE is a useful complement to the theorem prover Otter, with Otter searching for proofs and MACE looking for countermodels.Comment: 10 page

Non-linear unsteady wing theory, part 1. Quasi two-dimensional behavior: Airfoils and slender wings

The initial phases of a study of the large-amplitude unsteady aerodynamics of wings in severe maneuver are reported. The research centers on vortex flows, their initiation at wing surfaces, their subsequent convection, and interaction dynamically with wings and control surfaces. The focus is on 2D and quasi-2D aspects of the problem and features the development of an exact nonlinear unsteady airfoil theory as well as an approach to the crossflow problem for slender wing applications including leading-edge separation. The effective use of interactive on-line computing in quantifying and visualizing the nonsteady effects of severe maneuver is demonstrated. Interactive computational work is now possible, in which a maneuver can be initiated and its effects observed and analyzed immediately

Encapsulation for Practical Simplification Procedures

ACL2 was used to prove properties of two simplification procedures. The procedures differ in complexity but solve the same programming problem that arises in the context of a resolution/paramodulation theorem proving system. Term rewriting is at the core of the two procedures, but details of the rewriting procedure itself are irrelevant. The ACL2 encapsulate construct was used to assert the existence of the rewriting function and to state some of its properties. Termination, irreducibility, and soundness properties were established for each procedure. The availability of the encapsulation mechanism in ACL2 is considered essential to rapid and efficient verification of this kind of algorithm.Comment: 6 page