摘要:

A generalised approach is presented for the study of a computer-controlled queuing system with general input, ‘first-come-first-served’ queue discipline and multiple servers with feedback for either exponential servers or constant service times. Two generating functions for the state probabilities of the system corresponding to the two different types of service times are derived. Further, necessary and sufficient conditions for the existence of statistical equilibrium of the computer-controlled queuing system are obtained from the generating functions. The results obtained here generalise many results previously obtained by other workers.

DOI:10.1049/piee.1971.0257

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The paper presents two formulas for the determination of the waiting-time distribution in a computer-controlled queuing system with Poisson input, multiple-exponential servers and first-come-first-served queue discipline. The formulas obtained are expressed in terms of the stationary-state probabilities of the computer-controlled queuing system. One of the formulas is derived by means of the formula of total proability and the other is derived by the use of the theory of Markov chains. It is shown that, by virtue of a limiting process, the first formula obtained in the paper yields the waiting-time distribution in the conventional queuing system without computer control. Furthermore, application of the two formulas for the determination of waiting-time distribution is illustrated by an example.

DOI:10.1049/piee.1971.0258

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The organisation of a very large random-access computer store which uses redundancy in the form of error-correcting codes is described. The improvements in manufacturing yield which can be achieved by means of such redundancy are emphasised in the form of examples. However, with typical basic store sizes in the capacity range 107−108bits, some of the most significant improvements in manufacturing yield are achieved by programmed assembly which makes use of the ease of testability of such redundant systems. The conclusion is that widespread use of the proposed technique of design and manufacture can result in significant savings, both to designer and customer.

DOI:10.1049/piee.1971.0260

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Three methods for measuring the source and drain resistance of m.o.s. transistors operating in the unsaturated region are described. The results obtained on a number of simple m.o.s. transistors are presented to illustrate and compare each method and to indicate the significance of such measurements.

DOI:10.1049/piee.1971.0261

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Efficient thermal-energy storage requires effective thermal insulation. From a consideration of the possible heat-transfer modes, the requirements for a thermal barrier can be deduced. In a good conventional thermal insulation, most of the heat transfer takes place by conduction through the gas (air) in the insulation voids, the conductivity of the ‘still’ gas representing the limiting performance of such a material. It follows that a better performance can be obtained only by reducing this gas-conducted heat by having voids smaller than the molecular mean-free path (‘microporous’), by replacing the air by a low-conductivity gas or by partially evacuating the insulation.

DOI:10.1049/piee.1971.0263

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The paper deals with the applicability of unified machine theory to electrical machines where space harmonics can not be neglected. It is shown that there exists cases where a linear transformation can de determined to transform the set of time-depended linear differential equations for a machine at constant speed into a set of linear time-invariant differential equations, even if space harmonics are taken into considertation. A criterion for applicability is presented that involves the number of phases, the number of harmonics and the order of the harmonics that have to be considered.

DOI:10.1049/piee.1971.0264

出版商:IEE    

年代:1971

数据来源: IET

摘要:

An analytical study is described of the magnetic-field system in a d.c. linear motor. The equations derived are solved by numerical techniques based on a finite-difference approximation. A modification of existing methods is adopted to deal with heterogeneous regions of permeability. The computed flux profiles are shown to compare favourably with experimental results obtained on a 2-pole machine, including the effects of armature reaction. The results are used in tahe derivation of the developed force and dynamic characteristics of a loaded machine, and the theoretical results are again shown to agree closely with experimental results.

DOI:10.1049/piee.1971.0265

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The paper describes the design of a microalternator in which negative-resistance devices are employed to obtain representative constants of the model's rotor circuits. Dimensional scaling in assessing the parameters of model alternators is reviewed. Methods of calculating the model's principal constants from design data are outlined for a machine of salient-pole-rotor construction. Core and short-circuit losses are examined, and the choice of design criteria is discussed. Test results for a machine of salient-pole construction are given which compare very favourably with the constants derived from design considerations. Attention is also given to the special facilities which are provided by the time-constant regulator and other associated auxiliary equipment.

DOI:10.1049/piee.1971.0266

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Methods of modelling power systems in the study of the system transient behaviour are reviewed. Six machine models of varying complexity are developed from the fundamental machine equations. Factors in the form of the machine equations, which critically influence the economy of solution, are identified, The relationship between the machine and system equations is examined in relation to the digital solution of multimachine problems, and generalised methods of solution of the equations are outlined. Comparisons are made between results obtained from the range of machine models and those obtained from full-scale fault-throwing tests on the public supply system. In one case, a single machine connected to a system of high capacity is modelled, while, in the second example, two 60 MW machines connected to a large mulrimachine system is modelled. Both non-pole-slipping and pole-slipping tests for the case of the 2-machine system are examined, in which a machine marginally remained in synchronism and marginally lost synchronism, respectively. It is shown that models in which subtransient phenomena are simulated, but in which some transformer voltages in the stator equations, together with subtrasient saliency, are neglected, provide an adequate and economical model for system disturbances, including those in which the machine may fall from synchronism.

DOI:10.1049/piee.1971.0267

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The paper presents a new technique of analysis. Equivalent circuits, which normally omit altogether the asymmetrical and 2nd-harmonic armature-current components, are made to give the complete solution including the said components by applying theorems which are well known for their simplifying effect. In the first alternative, Norton's theorem is used to replace the 3-phase armature-voltage source by equivalent current sources on the direct and quadrature axes. The appropriate axis loads presented by the rest of the machine are connected to the current sources. Thus, appropriately energised equivalent circuits are obtained which give the complete solution. In the second alternative, the ‘effective’ 2-axis armature-voltage source, for short-circuit conditions, is determined by the constant-flux-linkage theorem. Then, by Thévenin's theorem, the appropriately energised equivalent circuits are obtained which again give the complete solution.

DOI:10.1049/piee.1971.0268

出版商:IEE    

年代:1971

数据来源: IET