ALDAS is a versatile program which has been in use for a number of years and which uses diffraction theory for computing the effects of a conducting structure on the RF performance of an antenna mounted on or off the ...
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ALDAS is a versatile program which has been in use for a number of years and which uses diffraction theory for computing the effects of a conducting structure on the RF performance of an antenna mounted on or off the structure. Geometrical Theory of Diffraction consists of a number of solutions to canonical problems such as diffraction at an edge, at cone tips, creeping waves et cetera. Since these are solutions to canonical problems, compromises have to be made between runtime and complexity on one hand and accuracy on the other. The major decisions in writing the program were to use a structure model which included canonical shapes rather than the computer intensive solution of fitting NURBS to a surface and to write in FORTRAN using a reliable compiler (Salford FTN77). These decisions reflect an engineering approach to the software and mean that the program can be used on a desktop machine rather than a more expensive workstation. ALDAS can carry out the computation of radiation patterns (nearfield and farfield) and isolation between antennas. At each stage in the model build, decisions have had to be taken which trade-off complexity, runtime and accuracy. The purpose of this paper is to review the aspects of accuracy and comment on the effects as far as the user is concerned.
The main aim of this paper is to present an understanding of the nature, purpose and future developments in intelligent object-oriented modelling arising from a research project being carried out by the Control and Co...
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The main aim of this paper is to present an understanding of the nature, purpose and future developments in intelligent object-oriented modelling arising from a research project being carried out by the Control and computer Aided Engineering (CCAE) research group at Swansea. Three important concepts for engineering modelling are emphasised: the independence of modelling from simulation;the object-oriented paradigm;knowledge-based systems. It is argued that intelligent technologies are natural tools for multidisciplinary engineering applications and are not only suited to qualitative approaches but also to quantitative methodologies.
The paper describes a framework for the modelling and simulation of hybrid systems and the implementation of the strategy in the real-time Expert System tool, G2. The strategy is predicated on three key notions: hybri...
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The paper describes a framework for the modelling and simulation of hybrid systems and the implementation of the strategy in the real-time Expert System tool, G2. The strategy is predicated on three key notions: hybrid model base, interactions between dissimilar model elements, and hybrid simulation. The combination of a hybrid model structure, incorporating Grafcets, equations, rules and objects, with the real-time features of G2 is shown to be an efficient vehicle for the integration of process functions such as supervisory control, sequential control, scheduling, fault monitoring and optimisation.
The paper describes a framework for the modelling and simulation of hybrid systems and the implementation of the strategy in the real-time Expert System tool, G2. The strategy is predicated on three key notions: hybri...
The paper describes a framework for the modelling and simulation of hybrid systems and the implementation of the strategy in the real-time Expert System tool, G2. The strategy is predicated on three key notions: hybrid model base, interactions between dissimilar model elements, and hybrid simulation. The combination of a hybrid model structure, incorporating Grafcets, equations, rules and objects, with the real-time features of G2 is shown to be an efficient vehicle for the integration of process functions such as supervisory control, sequential control, scheduling, fault monitoring and optimisation.
The emergence and progress of optical technologies have enabled them to have a profound effect in telecommunications and consumer electronics and also for optical sensing and measurements. To exploit fully the potenti...
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The emergence and progress of optical technologies have enabled them to have a profound effect in telecommunications and consumer electronics and also for optical sensing and measurements. To exploit fully the potential of the available faster transmission rates, higher bandwidths, and low transmission losses available with optics, the aim is to increase the capability of optical systems by introducing approaches based on new physical principles and on the optimization of such devices. Analytic modelling techniques are available, but however, lightwave systems do not lend themselves well to such models, due to the frequent use of unrealistic assumptions and design restrictions in some cases. A better approach is computer aided modelling which can be flexible and has been developed for the range of lightwave systems, with the potential to take into account important systems features. A wide range of computer-aided design and simulation packages have been developed for a considerable number of photonic devices. modelling work carried out on MMI (multimode interference) devices is presented, as representative of this.
The main aim of this paper is to present an understanding of the nature, purpose and future developments in intelligent object-oriented modelling arising from a research project being carried out by the Control and Co...
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The main aim of this paper is to present an understanding of the nature, purpose and future developments in intelligent object-oriented modelling arising from a research project being carried out by the Control and computer Aided Engineering (CCAE) research group at Swansea. Three important concepts for engineering modelling are emphasised: the independence of modelling from simulation; the object-oriented paradigm; knowledge-based systems. It is argued that intelligent technologies are natural tools for multidisciplinary engineering applications and are not only suited to qualitative approaches but also to quantitative methodologies.
Traditionally, high frequency (HF) communications have been difficult to manage efficiently, mainly due to the variable nature of the propagating conditions. An automatic radio control system (ARCS) consisting of auto...
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Traditionally, high frequency (HF) communications have been difficult to manage efficiently, mainly due to the variable nature of the propagating conditions. An automatic radio control system (ARCS) consisting of automatic channel selection (ACS), automatic link establishment (ALE), and automatic link maintenance (ALM) will provide an automated system which will alleviate operator workload and improve communications availability at HF. Effective network management is fundamental to such a system. computermodelling and simulation is a powerful method for testing the suitability of parameter values and how they affect the operation of a communications systems. Various networks can be simulated highlighting the shortcomings and also the positive aspects of each configuration. This paper describes the current status and capabilities of a computer based ARCS network simulation designed to be used as an aid to developing the ARCS specification. It also presents some initial results.
There has been great interest in trying to model plasma growth in practical discharge devices. The various numerical methods that have been used in fluid simulation codes and in the hybrid model of Boeuf and Pitchford...
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There has been great interest in trying to model plasma growth in practical discharge devices. The various numerical methods that have been used in fluid simulation codes and in the hybrid model of Boeuf and Pitchford are described and compared. Hybrid techniques combining Monte Carlo and fluid models show a great deal of promise although they make demands on computer time. With the enormous increase in computing power that has become available, however, a purely Lagrangian Monte Carlo calculation is still not feasible. The development of multiprocessor systems may change the situation.
The elements of a flexible manufacturing system include workstations, load/unload stations, transport, pallets, fixtures, tools, buffers/store and control computers. In embarking on a simulation, the system should be ...
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The elements of a flexible manufacturing system include workstations, load/unload stations, transport, pallets, fixtures, tools, buffers/store and control computers. In embarking on a simulation, the system should be defined and the model validated. A stochastic discrete next event simulation is usually used. simulation provides system behavior prior to its construction or provides non-invasive study of an existing system and produces awareness of the problem as well as acting as a communication aid. A simulation can be developed graphically or in a general purpose language or by a simulation package which is a set of common routines or by a generic model or by a data driven method. The trend in simulation development is towards easiness in use and understanding of the output.
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