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Making use of Contributions to an international congress on dynamic modelling and control of national economies, the author tries to present a survey of the application of mathematical models and methods of control engineering in this field. He enters into the fascinating similarities of fields of tension in the economy to those in control engineering, and deals with macro-economic problems of control and, more specifically, of stabilizing and optimizing methods.

A simple dynamic model is developed that describes some of the important aspects of research and development projects. Its purpose is illustration of the applicability of dynamic modelling to understanding the key factors affecting R & D performance. The model recognizes the differences among real, perceived, and reported progress on the job. It also includes the effect of schedule pressures on productivity. Simulation results are presented that, among other things, illustrate the trade-off between meeting schedule and maintaining organizational stability, the effects of rapid problem detection and response, and the difficulties due to the intangible nature of R & D progress.

The paper describes some recent research on the dynamic modelling and control of dissolved oxygen (DO) and biochemical oxygen demand (BOD) in a nontidal river system. A simple ordinary differential equation model for DO-BOD interaction in a single reach of a river has been verified against field data obtained from the River Cam outside Cambridge in Eastern England. The major details of this model are outlined and it is then used as the basis for a series of control studies concerned with the operational regulation of sewage effluent discharges in order to maintain specified levels of in-stream DO in both single and multiple reach river systems.

A simplified theoretical model for the dynamics of a side-fired steam reformer is derived. Experimental work, designed to confirm the theoretical model, is described, and the use of the results in the design of a feed-forward/feedback control scheme for throughput changes is discussed. This scheme, implemented on an on-line computer, enables large throughput changes to be made with a minimum of disturbance to the plant and a minimum of effort by the plant operators. Results from a typical throughput change are presented.

A system that is to serve as a vehicle for testing models of language change is being programmed in JOVIAL. Inherent in the design of the system is the requirement that each member of a speech community be represented by a generation grammar and a recognition grammar. The units of interaction in a simulation are conversations. Grammar rules may be borrowed or lost by individuals during the course of a simulation. The rules themselves need not be limited to those suggested by a particular theory of language; also, they may refer to any or all levels of linguistic phenomena. Extralinguistic factors pertinent to language change may be incorporated in simulations.

This summer school organised by the Institute and co-sponsored by the Inter-University of Engineering Control at the University of Warwick, was a lively success. Fifty students and 12 lecturers attended. The tutorials were of immense value and the assistance given by the Research Students of the University was fully appreciated. The school would not have been the success it was without the great effort put in by Dr. M. T. G. Hughes and others at the University. The object of the school was to benefit engineers and others concerned with the analysis of dynamic systems and the application of this to the solution of Industrial problems. It achieved its object!

A dynamic model is described which contains the main elements influencing the behaviour of an a.c./d.c. link during the first few cycles after a disturbance. Particular importance is given to the representation of the a.c. system, convertor filters and automatic controls. A digital-computer program based on this model is used to investigate the behaviour of the convertors under 3-phase short-circuit fault conditions, with strong and weak a.c. systems. The program is also used to investigate the influence of conventional and equal-firing types of control on the convertor behaviour.