Verification of Random Graph Transformation Systems

In this paper we describe some statistical results obtained by the verification of random graph transformation systems (GTSs). As a verification technique we use over-approximation of GTSs by Petri nets. Properties we want to verify are given by markings of Petri nets. We also use counterexample-guided abstraction refinement approach to refine the obtained approximation. A software tool (Augur) supports the verification procedure. The idea of the paper is to see how many of the generated systems can be successfully verified using this technique.     

Design of a magnetostrictive (MS) actuator

Several advanced technologies are introduced in automotive applications. Higher energy density and dynamic performance are demanding new and cost-effective actuator structures. Magnetostriction (MS), change in shape of materials under the influence of an external magnetic field, is one of the advanced technologies. Good understanding of specific design constrains is required to define and optimize a magnetostrictive actuator. This paper presents parametrical analysis with magnetic simulation of a magnetostrictive actuator. Proposed actuator has been designed, and the performance has been evaluated on experimental rig. Strain, elongation of the shaft, of 1000 ppm at 10 A and a blocked force over 4500 N has been achieved with shaft of 8 mm diameter, made of Terfenol-D. Furthermore, the effect of pre-stress of the Terfenol-D shaft has been evaluated experimentally. The study shows that excellent features can be obtained by magnetostrictive materials for many advanced applications.     

On-the-fly Workload Prediction and Redistribution in the Distributed Timed Model Checker Zeus

In this work we present the on-the-fly workload prediction and redistribution techniques used in Zeus [Braberman, V., A. Olivero and F. Schapachnik, Zeus: A distributed timed model checker based on kronos, in: Workshop on Parallel and Distributed Model Checking, affiliated to CONCUR 2002 (13^th International Conference on Concurrency Theory), ENTCS 68 (2002), Braberman, V., A. Olivero and F. Schapachnik, Issues in Distributed Model-Checking of Timed Automata: building zeus, to appear in International Journal of Software Tools for Technology Transfer (2004)], a Distributed Model Checker that evolves from the tool Kronos [Daws, C., A. Olivero, S. Tripakis and S. Yovine, The Tool KRONOS, in: Proceedings of Hybrid Systems III, LNCS 1066 (1996), pp. 208–219].After reviewing why it is so hard to have good speedups in distributed timed model checking, we present the methods used to get promising results when verifying reachability properties over timed automata [Alur, R. and D. L. Dill, A theory of timed automata, Theoretical Computer Science 126 (1994) 183–235].     

PMaude: Rewrite-based Specification Language for Probabilistic Object Systems

We introduce a rewrite-based specification language for modelling probabilistic concurrent and distributed systems. The language, based on PMaude, has both a rigorous formal basis and the characteristics of a high-level rule-based programming language. Furthermore, we provide tool support for performing discrete-event simulations of models written in PMaude, and for statistically analyzing various quantitative aspects of such models based on the samples that are generated through discrete-event simulation. Because distributed and concurrent communication protocols can be modelled using actors (concurrent objects with asynchronous message passing), we provide an actor PMaude module. The module aids writing specifications in a probabilistic actor formalism. This allows us to easily write specifications that are purely probabilistic – and not just non-deterministic. The absence of such (un-quantified) non-determinism in a probabilistic system is necessary for a form of statistical analysis that we also discuss. Specifically, we introduce a query language called Quantitative Temporal Expressions (or QuaTEx in short), to query various quantitative aspects of a probabilistic model. We also describe a statistical technique to evaluate QuaTEx expressions for a probabilistic model.     

Exogenous Probabilistic Computation Tree Logic

We define a logic EpCTL for reasoning about the evolution of probabilistic systems. System states correspond to probability distributions over classical states and the system evolution is modelled by probabilistic Kripke structures that capture both stochastic and non–deterministic transitions. The proposed logic is a temporal enrichment of Exogenous Probabilistic Propositional Logic (EPPL). The model-checking problem for EpCTL is analysed and the logic is compared with PCTL; the semantics of the former is defined in terms of probability distributions over sets of propositional symbols, whereas the latter is designed for reasoning about distributions over paths of possible behaviour. The intended application of the logic is as a specification formalism for properties of communication protocols, and security protocols in particular; to demonstrate this, we specify relevant security properties for a classical contract signing protocol and for the so–called quantum one–time pad.     

Bytecode Rewriting in Tom

In this paper, we present a term rewriting based library for manipulating Java bytecode. We define a mapping from bytecode programs to algebraic terms, and we use Tom, an extension of Java that adds pattern-matching facilities, to describe transformations. An originality of Tom is that it provides a powerful strategy language to express traversals over trees and to control how transformation rules are applied. To be even more expressive, we use CTL formulae as conditions and we show how their satisfiability can be ensured using the strategy formalism. Through small examples, we show how bytecode analysis and transformations can be defined in an elegant way. In particular, we outline the implementation of a ClassLoader parameterized by a security policy that restricts file access.     

Problem of reconstructing input signals under communication constraints

For a linear controllable system, the problem of reconstruction of all input signals, which are compatible with the measured signal, is considered. It is assumed that information can be transmitted in a processing center only via digital communication channel at discrete time instants, and the word length is limited. In this connection, there are encoding and decoding devices in the communication channel. For simplicity, the communication channel is assumed to be noiseless and delay-free. Defining relationships are obtained for the set of compatible input signals, as well as relationships between reconstruction precision, length of transmitted word and transmission frequency.     

Quantifier Elimination over Algebraically Closed Fields in a Proof Assistant using a Computer Algebra System

We propose a decision procedure for algebraically closed fields based on a quantifier elimination method. The procedure is intended to build proofs for systems of polynomial equations and inequations. We describe how this procedure can be carried out in a proof assistant using a Computer Algebra system in a purely skeptical way. We present an implementation in the particular framework of Coq and Maple giving some details regarding the interface between the two tools. This allows us to show that a Computer Algebra system can be used not only to bring additional computational power to a proof assistant but also to enhance the automation of such tools.     

Problem of optimal oscillator control for nulling its energy under bounded control action

Consideration was given to the problem of optimal control based on two performance criteria with the aim of full oscillator stopping from the initial state.     

A Petri Net Semantics of a Simple Process Algebra for Mobility

In this paper, we propose a structural translation of terms from a simple variant of the Klaim process algebra into behaviourally equivalent finite high level Petri nets. This yields a formal semantics for mobility allowing one to deal directly with concurrency and causality.     

Enantioselective, potentiometric membrane electrodes based on cyclodextrins for the determination of l-histidine

Four enantioselective, potentiometric membrane electrodes based on carbon paste impregnated with α-, β-, 2-hydroxyl-3-trimethylammoniopropyl-β-(as chloride salt) and γ-cyclodextrins (γ-CDs) are proposed for the assay of l-histidine (l-his). The proposed electrodes showed near-Nernstian response over l-his but not over d-histidine (d-his). The recovery of l-his in the presence of d-his was higher than 99.10% with R.S.D. lower than 0.1%. The surfaces of the electrodes are easily renewable by simply polishing on an alumina paper.     

Deadlock and starvation free reentrant readers-writers: A case study combining model checking with theorem proving

The classic readers-writers problem has been extensively studied. This holds to a lesser degree for the reentrant version, where it is allowed to nest locking actions. Such nesting is useful when a library is created with various procedures each starting and ending with a lock operation. Allowing nesting makes it possible for these procedures to call each other.We considered an existing widely used industrial implementation of the reentrant readers-writers problem. Staying close to the original code, we modelled and analyzed it using a model checker resulting in the detection of a serious error: a possible deadlock situation. The model was improved and checked satisfactorily for a fixed number of processes. To achieve a correctness result for an arbitrary number of processes the model was converted to a specification that was proven with a theorem prover. Furthermore, we studied starvation. Using model checking we found a starvation problem. We have fixed the problem and checked the solution. Combining model checking with theorem proving appeared to be very effective in reducing the time of the verification process.     

Multicast inference of temporal loss characteristics

Multicast-based inference has been proposed as a method of estimating average loss rates of internal network links, using end-to-end loss measurements of probes sent over a multicast tree. We show that, in addition to loss rates, temporal characteristics of losses can also be estimated. Knowledge of temporal loss characteristics has applications for services such as voip which are sensitive to loss bursts, as well as for bottleneck detection. Under the assumption of mutually independent, but otherwise general, link loss processes, we show that probabilities of arbitrary loss patterns, mean loss-run length, and even the loss-run distribution, can be recovered for each link. Alternative estimators are presented which trade-off efficiency of data use against implementation complexity. A second contribution is a novel method of reducing the computational complexity of estimation, which can also be used by existing minc estimators. We analyse estimator performance using a combination of theory and simulation.     

Construction of invariant ellipsoids in the stabilization problem for a wheeled robot following a curvilinear path

The synthesis control problem for the plane motion of a wheeled robot is studied. The goal of the control is to bring the robot to an assigned curvilinear trajectory and to stabilize its motion along it in the presence of phase and control constraints. For a synthesized control law, invariant ellipsoids—quadratic approximations of the attraction domains of the target trajectory—are constructed, which allow one to check in the course of the robot motion whether the control law can stabilize motion along the current trajectory segment. To take into account constraints on the control, methods of absolute stability theory are applied. The construction of the invariant ellipsoids reduces to solving a system of linear matrix inequalities.     

Optimization of boundary control at one end of a string in the presence of a model nonlocal condition

The paper is devoted to problems of optimal boundary control of string vibrations under nonlocal conditions that relate values of string displacement or its derivative at the boundary point with their values at the interior point. The solutions for all problems of boundary control are obtained in explicit analytic form.     

Identification of frequency of a shifted sinusoidal signal

The article deals with the issue of identification of an unknown frequency of a shifted sinusoidal signal y(t) = σ ₀ + σ sin(ωt + ?). A new approach taken to estimate the frequency of a shifted sinusoidal signal is suggested, which is a robust approach relative to undetermined disturbances present in the measurement of a useful signal. In contrast to known analogs, the given approach permits controlling the time of estimation of the unknown frequency ω. The dimension of the identification algorithm suggested is less than that of known analogs.