L.J. van Bokhoven

Object-oriented modelling and specification using SHE

Industry is facing a crisis in the design of complex hardware/software systems. Due to the increasing complexity, the gap between the generation of a product idea and the realisation of a working system is expanding rapidly. To manage complexity and to shorten design cycles, industry is forced to look at system-level languages towards specification and design. The (formal) system-level modelling language called POOSL is very expressive and is able to model dynamic hard real-time behaviour and to (visually) capture static (architecture and topology) structure in an object-oriented fashion. The language integrates a process part, based on the process algebra CCS, with a data part, based on the concepts of traditional object-oriented programming languages and it is equipped with a formal semantics. Currently, a number of automated software tools (model editing, simulator and compiler tools) are available in an environment called SHESim. These tools allow visual entry of structure and topology of the system, whereas dynamic behaviour of individual processes is expressed in an expressive imperative language. The formal semantics of POOSL provides a solid basis for the application of verification and performance analysis techniques and establishing a rigorous connection to existing analysis tools.

Software synthesis for system level design using process execution trees

Software synthesis for system level design languages becomes feasible because the current technology, pricing and application trends will most likely alleviate the industrial emphasis on real-time operating systems minimisation. Automatic code generation also becomes necessary, because of increasing product complexity and decreasing design time. This paper discusses software synthesis for a realistic system level design language, to generate an executable model for implementation, simulation and verification purposes. A completely automatic mapping of both the architectural aspects and data objects is shown, including real-time garbage collection. Process execution trees (PETs) are introduced to schedule real-time, concurrent processes. This paper explains the functioning of these self-modifying data structures based on the operational semantics of POOSL (Parallel Object-Oriented Specification Language). Process execution trees are generally applicable to other process algebras as well (e.g. CCS, CSP, ACP), and follow quite naturally from the inference rules of these algebras.

Generation of zonal flows in rotating fluids and magnetized plasmas

The spontaneous generation of large-scale flows by the rectification of small-scale turbulent fluctuations is of great importance both in geophysical flows and in magnetically confined plasmas. These flows regulate the turbulence and may set up effective transport barriers. In the present contribution the generation of zonal flows will be illustrated in a simple fluid experiment performed in a rotating container with radial symmetric bottom topography. An effective mixing that homogenizes the potential vorticity in the fluid layer will lead to the replacement of the high-potential vorticity near the centre with low potential vorticity from the outside, which will imply the formation of a large-scale flow. The experimental results are supported by direct numerical solutions of the quasi-geostrophic vorticity equation in the β-plane approximation modelling the experimental situation. The analogy to large-scale flow generation in drift-wave turbulence dynamics in magnetized plasma is briefly discussed.

Modelling the Formation of Large Scale Zonal Flows in Drift Wave Turbulence in a Rotating Fluid Experiment

The formation of large‐scale flows — zonal flows — is demonstrated in a laboratory experiment with a fluid in a rotating container with bottom topography. The fluid is efficiently stirred by external forcing. The flow generation is explained by mixing and homogenization of the potential vorticity. By employing the analogy between drift wave dynamics in a magnetized plasma and flow dynamics in the rotating tank the results can be considered as a model for zonal flow generation in drift wave turbulence.