Occam—A programming language for multiprocessor systems

The features of concurrency provide important concepts for problem solving in a wide range of application areas. Many languages have now been developed to support this approach, with various notations being proposed. Occam is a programming language which supports concurrency using the process as its program structure, and provides synchronous communication between these processes. This paper presents the main features of occam and illustrates its use through various examples.     

The programming language GCLA — A definitional approach to logic programming

We present a logic programming language, GCLA^*** (Generalized horn Clause LAnguage), that is based on a generalization of Prolog. This generalization is unusual in that it takes a quite different view of the meaning of a logic program—a “definitional” view rather than the traditional logical view. GCLA has a number of noteworthy properties, for instance hypothetical and non-monotonic reasoning. This makes implementation of reasoning in knowledge-based systems more direct in GCLA than in Prolog. GCLA is also general enough to incorporate functional programming as a special case. GCLA and its syntax and semantics are described. The use of various language constructs are illustrated with several examples.     

Parallel nonlinear decoupling for process control — A NARMAX approach

The contribution of this paper is twofold. First, we focus on the application of a particular NARMAX (nonlinear ARMAX) model representation based on local models for adaptive decoupling. Second, in order to improve the robustness of the adaptive control algorithm we introduce a diagonal PI-controller in parallel with the adaptive decoupler. These controllers are separated in the frequency domain, such that the decoupler and PI-controller takes care of control actions at higher and lower frequencies, respectively. The parallel control structure supports incremental control design, in the sense that improved process knowledge is used to successively upgrade control performance. The concept is illustrated by a semi-realistic simulation example.     

Max-plus-linear model-based predictive control for constrained hybrid systems：linear programming solution

In this paper, a linear programming method is proposed to solve model predictive control for a class of hybrid systems. Firstly, using the （max, ＋） algebra, a typical subclass of hybrid systems called max-plus-linear （MPL） systems is obtained. And then, model predictive control （MPC） framework is extended to MPL systems. In general, the nonlinear optimization approach or extended linear complementarity problem （ELCP） were applied to solve the MPL-MPC optimization problem. A new optimization method based on canonical forms for max-min-plus-scaling （MMPS） functions （using the operations maximization, minimization, addition and scalar multiplication） with linear constraints on the inputs is presented. The proposed approach consists in solving several linear programming problems and is more efficient than nonlinear optimization. The validity of the algorithm is illustrated by an example.     

ADDS—a dialogue development system for the Ada programming language

A dialogue development system for the Ada programming language is described. The system supports the production of multi-level adaptable interfaces and provides the following features: input validation, user recovery/backtracking, in-depth help facilities, user-performance monitoring and a variety of user interface specification languages. In addition, development tools are provided that enable dialogue specific software to be automatically generated from the constituent specifications. Considerations are given to the use of multi-level interfaces and the employment of such systems in studying user adaptability and learning. The architecture of ADDS is described and some simple examples of its use are given. Although ADDS is designed for, and implemented in, Ada, it is structured in a manner that will make the features it supports more widely applicable.     

Chemical process control—A new technique for adaptive tuning of controllers†

This paper presents a new technique for determining the optimum settings of the conventional two-mode and three-mode controllers. The procedure which utilizes the practically available on-line closed loop data is an extension of the classical work of Ziegler and Nichols (1942). The advantages of the present method over that of Ziegler and Nichols are (i) that it does not require the process to undergo sustained oscillations, (ii) that the tuning constants are determined iteratively (and not by hit-and-miss technique) thereby making the tuning adaptive in nature and (iii) that it is possible to select a criterion of optimality other than the usual 1:4 decay ratio.     

A fuzzy PLC with gain-scheduling control resolution for a thermal process – a case study

This paper presents a case study on the practical implementation of a fuzzy-PLC system for a thermal process. The theoretical study indicates that the inferior performance of fuzzy-controlled processes around a reference point is often caused by insufficient resolution of the fuzzy inference. The limitations of ladder logic cannot support complex algorithms for resolution improvement. A simple gain adaptation method is presented here, to achieve smooth fuzzy control, that can be easily implemented in a PLC system. Real-time experiments on an unidentified thermal process show the effectiveness of the approach, as well as the robustness of the fuzzy controller with respect to the time-varying features of the process.     

A framework for process–solution analysis in collaborative learning environments

One of the most challenging aspects of computer-supported collaborative learning (CSCL) research is automation of collaboration and interaction analysis in order to understand and improve the learning processes. It is particularly necessary to look in more depth at the joint analysis of the collaborative process and its resulting product. In this article, we present a framework for comprehensive analysis in CSCL synchronous environments supporting a problem-solving approach to learning. This framework is based on an observation–abstraction–intervention analysis life-cycle and consists of a suite of analysis indicators, procedures for calculating indicators and a model of intervention based on indicators. Analysis indicators are used to represent the collaboration and knowledge building process at different levels of abstraction, and to characterize the solution built using models of the application domain, the problems to solve and their solutions. The analysis procedures combine analysis of actions and dialogue with analysis of the solution. In this way, the process and the solution are studied independently as well as together, enabling the detection of correlations between them. In order to exemplify and test the framework, the methodological process underlying the framework was followed to guide the implementation of the analysis subsystems of two existing CSCL environments. In addition, a number of studies have been conducted to evaluate the framework's approach, demonstrating that certain modes of collaborating and working imply particular types of solutions and vice versa.     

RASP—A language with operations on fuzzy set

At the Center for Multidisciplinary Studies, University of Belgrade, Yugoslavia, a high level language for easily manipulating fuzzy set operations was developed. In this paper, after a brief introduction to the theory of fuzzy sets, some features and possibilities are described from the user point of view, and an application in picture enhancement is shown. The language presented was written in BASIC, thus any microcomputer, for personal/home use, should be able to execute RASP.     

A probabilistic solution of robust H∞ control problem with scaled matrices

This paper addresses the robust H_∞ control problem with scaled matrices. It is difficult to find a global optimal solution for this non-convex optimisation problem. A probabilistic solution, which can achieve globally optimal robust performance within any pre-specified tolerance, is obtained by using the proposed method based on randomised algorithm. In the proposed method, the scaled H_∞ control problem is divided into two parts: (1) assume the scaled matrices be random variables, the scaled H_∞ control problem is converted to a convex optimisation problem for the fixed sample of the scaled matrix and a optimal solution corresponding to the fixed sample is obtained; (2) a probabilistic optimal solution is obtained by using the randomised algorithm based on a finite number N optimal solutions, which are obtained in part (1). The analysis shows that the worst case complexity of proposed method is a polynomial.     

A problem evolution algorithm with linear programming for the dynamic facility layout problem—A general layout formulation

Facility layout problems (FLPs) are quite common and important in many industries. This paper presents a mixed integer linear programming (MILP) model for the dynamic facility layout problem, which is a generalization of several special cases of FLPs studied in recent years. A new evolutionary meta-heuristic framework, named as the problem evolution algorithm (PEA), is developed as a general solution approach for FLPs. Computational experiments show that the PEA combined with the linear programming (LP), called PEA-LP in short, performs well in various types of FLPs. In addition, a new polyhedral inner-approximation method is proposed based on secant lines for the linearization of the non-linear constraint for department area requirements. This new method guarantees that the actual department area is always greater than or equal to the required area within a given maximum deviation error. Furthermore, two new symmetry-breaking constraints which help to improve the computational efficiency of the MILP model are also introduced. Computational experiments on several well-known problem instances from the literature are carried out to test the DFLP-FZ and the PEA-LP with promising results.     

A formal model for access control with supporting spatial context

There is an emerging recognition of the importance of utilizing contextual informa tion in authorization decisions. Controlling access to resources in the field of wireless and mobile networking require the definition of a formal model for access control with supporting spatial context. However, traditional RBAC model does not specify these spatial requirements. In this paper, we extend the existing RBAC model and propose the SC-RBAC model that utilizes spatial and location-based information in security policy definitions. The concept of spatial role is presented, and the role is assigned a logical location domain to specify the spatial boundary. Roles are activated based on the current physical position of the user which obtained from a specific mobile terminal. We then extend SC-RBAC to deal with hierarchies, modeling permission, user and activation inheritance, and prove that the hierarchical spatial roles are capable of constructing a lattice which is a means for articulate multi-level security policy and more suitable to control the information flow security for safety-critical location-aware information systems. Next, constrained SC-RBAC allows express various spatial separations of duty constraints, location-based cardinality and temporal constraints for specify fine-grained spatial semantics that are typical in location-aware systems. Finally, we introduce 9 invariants for the constrained SC-RBAC and its basic security theorem is proven. The constrained SC-RBAC provides the foundation for applications in need of the constrained spatial context aware access control.     

A new control method for the relative dielectric constant of 1–3 piezoelectric composites realized with the LIGA process

 A plasma treatment for controlling the relative dielectric constant (ɛ_r) of fine-scale lead zirconate titanate (PZT) rods was developed. This new method made it easy to control ɛ_r of 1-3 piezoelectric composites, which were made up of fine-scale PZT rods in epoxy resin. The PZT rods were fabricated using the LIGA process, realizing an array of PZT rods with a cross section, height and volume fraction of 25 μm square, 250 μm and 25%, respectively. The new method consists of a plasma treatment applied before sintering of the PZT rods. By controlling the output RF power and duration of the plasma treatment, ɛ_r could be controlled between 250 and 400. Although extended plasma etching reduced ɛ_r, there were no changes in the piezoelectric properties and no defects in the sintered body. The ability to control ɛ_r of piezoelectric composites allows good electrical impedance matching with the electric circuit of diagnostic systems, thereby reducing signal transmission losses. Changing ɛ_r by varying the piezoelectric material or the sintering conditions requires lengthy process optimization. In contrast, controlling ɛ_r to establish a good impedance match can be done relatively easily with this new plasma technique because the piezoelectric properties are not affected.