GRL: A Specification Language for Globally Asynchronous Locally Synchronous Systems

International audienceA GALS (Globally Asynchronous, Locally Synchronous) system consists of several synchronous subsystems that evolve concurrently and interact with each other asynchronously. Most formalisms and design tools support either the synchronous paradigm or the asynchronous paradigm but rarely combine both, which requires an intricate modeling of GALS systems. In this paper, we present a new language, called GRL (GALS Representation Language) designed to model GALS systems in an abstract and versatile manner for the purpose of formal verification. GRL has formal semantics combining the synchronous reactive model underlying dataflow languages and the asynchronous concurrent model underlying process algebras. We present the basic concepts and the main constructs of the language, together with an illustrative example

Novel muon imaging techniques

Owing to the high penetrating power of high-energy cosmic ray muons, muon imaging techniques can be used to image large bulky objects, especially objects with heavy shielding. Muon imaging systems work just like CT scanners in the medical imaging field—that is, they can reveal information inside of a target. There are two forms of muon imaging techniques: muon absorption imaging and muon multiple scattering imaging. The former is based on the flux attenuation of muons, and the latter is based on the multiple scattering of muons in matter. The muon absorption imaging technique is capable of imaging very large objects such as volcanoes and large buildings, and also smaller objects like spent fuel casks; the muon multiple scattering imaging technique is best suited to inspect smaller objects such as nuclear waste containers. Muon imaging techniques can be applied in a broad variety of fields, i.e. from measuring the magma thickness of volcanoes to searching for secret cavities in pyramids, and from monitoring the borders of countries checking for special nuclear materials to monitoring the spent fuel casks for nuclear safeguards applications. In this paper, the principles of muon imaging are reviewed. Image reconstruction algorithms such as Filtered Back Projection and Maximum Likelihood Expectation Maximization are discussed. The capability of muon imaging techniques is demonstrated through a Geant4 simulation study for imaging a nuclear spent fuel cask

Formal Modeling and Verification of GALS Systems Using GRL and CADP

The GALS (Globally Asynchronous, Locally Synchronous) paradigm is a prevalent approach to design distributed synchronous subsystems that communicate with each other asynchronously. The design of GALS systems is tedious and error-prone due to the complexity of architectures and high synchronous and asynchronous concurrency involved. This paper proposes a model-based approach to formally verify such systems. Specifications are written in GRL (GALS Representation Language), dedicated to model GALS systems with homogeneous syntax and formal semantics. We present a translation from GRL to LNT, a value-passing process algebra with imperative flavour. The translation is automated by means of the GRL2LNT tool, making possible the analysis of GRL specifications using the CADP toolbox. We illustrate our approach with an access management system for smart parking based on distributed software systems embedded in programmable logic controllers

Suitability of high-pressure xenon as scintillator for gamma ray spectroscopy

In this paper we report the experimental study of high-pressure xenon used as a scintillator, in the context of developing a gamma ray detector. We measure a light yield near 2 photoelectrons per keV for xenon at 40 bar. Together with the light yield, we also measured an energy resolution of ~9% (FWHM) at 662 keV, dominated by the statistical fluctuations in the number of photoelectrons.Comment: 15 pages, 11 figure

GRL: A Specification Language for Globally Asynchronous Locally Synchronous Systems (Syntax and Formal Semantics)

A GALS (Globally Asynchronous, Locally Synchronous) system consists of a set of synchronous subsystems executing concurrently and interacting using an asynchronous communication scheme. Such systems involve a high degree of synchronous and asynchronous concurrency which makes challenging the design and debugging of applications. The use of formal methods in the design process helps designers to master that complexity and to build strong confidence in the correctness of these, usually safety-critical, systems. This report presents GRL (GALS Representation Language), a new formal language to specify GALS system for the purpose of formal verification, to provide design process with efficiency and correctness. GRL has a user-friendly syntax close to classical programming languages and an operational semantics combining the synchronous reactive paradigm inspired by classical data-flow languages and the asynchronous paradigm inspired by value-passing process algebras.Un système GALS (Globalement Asynchrone, Localement Synchrone) est composé d'un ensemble de sous-systèmes synchrones qui s'exécutent de manière concurrente suivant un schéma de communication asynchrone. De tels systèmes impliquent un haut degr'de concurrence synchrone et asynchrone, ce qui rend difficile la conception et le débogage des applications à cause du non-déterminisme des communications. L'intégration des méthodes formelles dans la procédure de conception aide les concepteurs à maîtriser cette complexité et à garantir la sûreté de ces systèmes, souvent critiques. Ce rapport présente GRL(GALS Representation Language), un nouveau langage formel pour la spécification des systèmes GALS afin de les vérifier formellement, pour rendre le processus de conception sûr et efficace. GRL possède une syntaxe conviviale, proche des langages de programmation classiques, et une sémantique opérationnelle qui combine le modèle synchrone inspiré de la programmation par flot de données et le modèle asynchrone inspiré des algèbres de processus

Foreword

This work reports on the performances of ohmic contacts fabricated on highly p-type doped 4H-SiC epitaxial layer selectively grown by vapor-liquid-solid transport. Due to the very high doping level obtained, the contacts have an ohmic behavior even without any annealing process. Upon variation of annealing temperatures, it was shown that both 500 and 800 °C annealing temperature lead to a minimum value of the Specific Contact Resistance (SCR) down to 1.3×10−6 Ω⋅cm2. However, a large variation of the minimum SCR values has been observed (up to 4×10−4 Ω⋅cm2). Possible sources of this fluctuation have been also discussed in this paper