摘要:

A processor-controlled packet-store-and-forward data-communication system is described and performance figures are presented. The philosophy of the system is characterised by the use of a route-search packet to establish the availability of both a route through the network and the destination terminal before the message data is accepted by the network. Subsequent message-data packets are constrained to follow the path established by the route search and are maintained in correct sequence by a comprehensive acknowledgment-and-signalling procedure. This also provides the facility of error correction by retransmission, and is the basis of a convenient method for the control of buffer storage within the network. The exchange implementation comprises a control computer operating in conjunction with link terminal units that are dedicated to the control of the input and output links of the exchange and to packet assembly and checking functions. Each of these units consists of a small autonomous microcomputer module controlled by a changeable microprogram. They can thus be readily adapted to accommodate the characteristics of the particular links and error-control facilities employed.

DOI:10.1049/piee.1972.0334

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Tests of a simple m.o.s. integrated circuit at elevated temperatures have previously exposed substantial negative shifts of threshold voltage in those transistors operated at a negative gate voltage. Some of the results presented in an earlier paper are now reprocessed to yield a simple mathematical model of the shift observed on one of the transistors. The model provides an improved basis for the prediction of long-term trends under the stresses of normal service life.

DOI:10.1049/piee.1972.0335

出版商:IEE    

年代:1972

数据来源: IET

摘要:

A linear discrete-time network (e.g. a digital filter) of the minimum-phase type is characterised by having a transfer function with poles and zeros all located outside the unit circle in the z−1plane. In the paper, the Cauchy integral formula is applied to this transfer function for values of z−1on the unit circle, and various sets of gain-phase relations are thereby obtained for the network. It is also shown that, when the sampling period approaches zero, these relations reduce to the well known gain-phase relations of a linear continuous-time network of the minimum-phase type.

DOI:10.1049/piee.1972.0337

出版商:IEE    

年代:1972

数据来源: IET

摘要:

A new form of a linear reluctance motor is described, comprising two flat rectangular plates of mild steel separated by a small airgap by means of linear bearings. One plate, which is fixed, acts as the stator, which accommodates a 3-phase distributed winding. Small square-cross-section slots are cut on the inside stator surface with a 2-start lead on similar slots cut orthogonally on the moving plate (the armature). Linear displacement is achieved by controlling the phase of the excitation supply in relation to the points of minimum reluctance. The motor is capable of operating over displacements of 1 m, or more, with good positional accuracy and a relatively low speed. The basic performance of the machine is described, and theoretical figures are compared with the experimental results obtained on a prototype motor.

DOI:10.1049/piee.1972.0339

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Recent research by Coaton and Phillips has provided a precise explanation of the physical mechanism causing halogen separation in linear tungsten-halogen lamps burning at arbitrary angles from the horizontal. Further investigation has shown that the two components in an argon-nitrogen or krypton-nitrogen gas mixture will separate in angle-burning linear tungsten-halogen lamps, which would have serious consequences if the nitrogen was used as an arc suppressant. The proposed separation mechanism almost certainly applies to any component in the gas filling of a linear lamp which differs in mass or bond energy from the main component. It is also equally applicable to the gases and vapours in linear discharge lamps.

DOI:10.1049/piee.1972.0340

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Synchronous machines in pumped-storage stations and in industry are very often run up asynchronously. This starting procedure can be treated within the scope of the 2-axis theory with modified equivalent diagrams, irrespective of whether the poles are laminated or solid. All solid-iron parts of the rotor are accounted for in the modified equivalent diagrams. When working with the conventional characteristic quantities of the synchronous machine (conventional equivalent diagrams), however, the calculated torque differs widely from the measured value, not only numerically but throughout the whole curve pattern. The method described here can also be used for brushless synchronous machines. On the basis of many experiments, the characteristic features of asynchronous starting with and without diodes in the field circuit are discussed and formulated in theoretical terms.

DOI:10.1049/piee.1972.0341

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The paper describes a new range of tubular induction motors. Compared with the usual forms of tubular motors, in which the magnetic flux lies largely in planes that are parallel to the direction of motion, the new machines have flux paths lying transverse to this direction. Two winding arrangements are described; the first of these uses skewed coils that completely surround the secondary conductor, the second uses a double helical system. The excitation produced by these windings is in the form of a circumferentially modulated axially travelling wave, and an appropriate multilayer analysis using cylindrical geometry is presented. Experimental and theoretical results are given that show that the transverse-flux machine can provide more thrust than the conventional machine when the core-flux density is the limiting design factor.

DOI:10.1049/piee.1972.0342

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The principle on which the electric differential is based can be employed in a number of different ways, leading to low-power applications of an instrument or indicator type, which have been discussed earlier. The principle can be applied on the one hand, for example, to phase-angle meters, synchroscopes, phase-sequence indicators and, on the other hand, to devices which supply more than token loads and for which power requirements must be evaluated in greater detail, and these have not hitherto been described. When the stator of a salient-pole machine is doubly fed in a particular manner, the shaft rotates at a frequency equal to one half the difference between the angular frequencies of the two polyphase systems employed—the feature from which the term ‘differential’ derives. The present paper examines the behaviour of this device and establishes simple theoretical principles which lead to stationary- or quasistationary-performance equations on which further developments can be based.

DOI:10.1049/piee.1972.0343

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Many processes have dynamic responses which are dependent on the direction in which the response variable is moving. The effects of such nonlinear behaviour on the weighting-function model of the process obtained by crosscorrelation and on the difference-equation model obtained by a generalised least-squares procedure are determined theoretically for a process with 1st-order dynamics perturbed with pseudorandom binary signals. The theory is confirmed by results from a hybrid-computer simulation, and computer-simulated results for processes with 2nd-order dynamics are also presented. Experimental work on two pilot-scale processes with direction-dependent dynamics is reported, and two further examples from the literature are examined.

DOI:10.1049/piee.1972.0350

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The attainment of diagonal dominance in an inverse Nyquist array of 2-variable control systems is examined for constant matrix compensation placed in the forward path. A quadratic inequality is obtained from Gershgorin's inequality, and this leads directly to a simple graphical-design technique for achieving row diagonal dominance. A useful outcome of the method is that it reveals cases in which solutions of this form do not exist. Alternatively, when row dominance can be satisfied, the complete set of solutions is obtained.

DOI:10.1049/piee.1972.0351

出版商:IEE    

年代:1972

数据来源: IET