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.     

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.     

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].     

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.     

Concurrent Java Test Generation as a Search Problem

A Random test generator generates executable tests together with their expected results. In the form of a noise-maker, it seeds the program with conditional scheduling primitives (such as yield()) that may cause context switches. As a result different interleavings are potentially produced in different executions of the program. Determining a-priori the set of seeded locations required for a bug to manifest itself is rarely possible.This work proposes to reformulate random test generation of concurrent Java programs as a search problem. Hence, it allows applying a set of well known search techniques from the domain of AI to the input space of the test generator. By iteratively refining the input parameters fed to the test generator, the search process creates testing scenarios (i.e. interleavings) that maximizes predefined objective functions. We develop geneticFinder, a noise-maker that uses a genetic algorithm as a search method. We demonstrate our approach by maximizing two objective functions: the high manifestation rate of concurrent bugs and the exporting of a high degree of debugging information to the user. Experimental results show our approach is effective.     

Combinatorial methods for constructing bipartite uniform minimal quasicomplete graphs (symmetrical block designs)

Consideration was given to a specific family of bipartite graphs consisting of two disjoint subsets X and Y of vertices and characterized by that each vertex in X (Y) is connected to each of the remaining vertices in X (Y) by a unique path of length two passing through some vertex in Y (X). The prefix “quasi” reflects the fact that complete connection of the vertices is realized by paths of length two rather than by edges. The problem of constructing uniform minimal graphs with identical cardinalities of the subsets X and Y which is of practical interest for complex communication networks was discussed. It belongs to the class of combinatorial problems of construction of the so-called symmetrical block designs.     

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.     

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.     

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.     

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.     

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.     

Algorithms to construct suboptimal organization hierarchies

The problem of controlling an organization structure (hierarchy of organization control) was considered as that of discrete optimization, that is, minimization by selecting the permissible hierarchy of total costs of maintaining its managers. For the case of the so-called uniform functions of manager costs, the lower estimate of the costs of the optimal hierarchy was obtained allowing one, besides all other things, to determine approximately the main characteristics of the optimal hierarchy such as the number of managers, their norm of controllability, and so on. Quality of this lower estimate was studied, and effective algorithms to construct suboptimal hierarchies with costs slightly exceeding the optimal ones were proposed for some important cases.     

Comparison of the quantile and guaranteeing approaches to system analysis

The worst value of the quantile of the distribution of the linear loss function which depends on the uncertain stochastic parameters was compared with the maximum value of this function. The stochastic uncertainty is modelled by distributions from the Barmish class.     

Universal software packages to model the distributed-parameter systems

Consideration was given to the universal software packages for modeling objects and distributed-parameter systems obeying the partial differential equations. The packages may serve as important tools for industrial automation because the majority of industrial objects have distributed parameters. The review presented the results of comparing a number of commercial packages against a set of user-defined criteria. Its final part was devoted to some freeware packages. Conclusions were drawn, and recommendations for using the considered packages were given.     

Nexus VII: Relationships Between Architecture and Mathematics

Sylvie Duvernoy reports on the seventh international, interdisciplinary Nexus conference for architecture and mathematics. Point Loma Nazarene University, San Diego, USA 23-25 June 2008     

Operating ratio of the technical systems,subjected to failures

The original way of definition of operating ratio in view of reliability of the equipment of the control, time of the control over periodic checks and time of restoration is offered. The received results allow to define the best value of operating ratio of system both in view of, and without taking into account operational expenses.     

Equipment life time optimization with respect to operational expenses

The subject of investigations is the equipment operational model, where the operational expenses are represented by planned replacement expenses and losses due to failures. The two replacement strategies are considered: “planned replacement at the end of predetermined life time or after a failure” and “planned replacement at the end of predetermined life time.” In the second case only working capacity is restored after failure. The optimal lifetime value is shown to depend on the ratio of planned replacement expenses and losses due to failure. The rated conditions for the optimal equipment lifetime and for the gamma-percentile life are obtained providing the distribution of time to failure is determined by the Weibull law. The expediency of the equipment group replacement is discussed.