摘要:

Results of oblique soundings over a path from Delhi, India to Slough, England are presented. The modes of propagation are often ill-defined, but the maximum observed frequencies agree well with those deduced from measured ionospheric conditions at points along the path, using either the two-control-point method or a ray-tracing process. The study includes a discussion of measured angles of elevation and multipath time dispersions.

DOI:10.1049/piee.1969.0366

出版商:IEE    

年代:1969

数据来源: IET

摘要:

The printed circuit is now accepted as a convenient and economic method of interconnecting electronic components. However, the design of printed circuits (especially multilayer types) is both complicated and expensive. The system described here enables a logic or circuit diagram to be translated into a printed-circuit board within a few hours by using computer techniques. A milling machine is described which processes a standard printed-circuit board into the final circuit. However, if very large numbers of the same circuit are required, the machine can produce photographic masks to be used in the usual method of printing and etching of copper-clad laminates.

DOI:10.1049/piee.1969.0367

出版商:IEE    

年代:1969

数据来源: IET

摘要:

A relationship between the transformations of trees and the corresponding basic loop and cutset matrices is established, which facilitates generation of these matrices with respect to any other or all possible trees of a graph in a routine manner. These transformation matrices can be set up directly without resorting to a series of elementary transformations. This method of generating the basic loop and cutset matrices is based on the concept of a Lagrangian tree. A method for minimising the number of nonzero entries in a loopset matrix is also discussed. Finally, two new methods for realising a given matrix as a loop or cutset matrix are proposed. These methods of analysis and synthesis will be particularly useful in dealing with complex networks which are commonly encountered in communication systems, electrical and switching networks, and models of many other physical systems.

DOI:10.1049/piee.1969.0368

出版商:IEE    

年代:1969

数据来源: IET

摘要:

The first part of the paper deals with a combined experimental and analytical study on a 5 hp laboratory set. It establishes the way in which the transient negative-torque peak ↑R− varies with the residual voltage on the machine terminals at the time of reconnecting the supply, and the phase angle that could exist between this voltage and the supply voltage which is being reconnected. An approximate expression for the peak negative torque is developed, which helps to explain why the characteristics showing how ↑R− varies diverge significantly from what would be expected by simple reasoning. A 100hp motor is then considered, and the variation of ↑R− with the time delaytdin reconnecting is established. The effects of the load at which the motor is operating at the instant of supply disconnection and of external inertia are examined. Finally, for a range of machines from 100 to 2700hp, operating at various loads and with various external inertias, patterns of ↑R−/tdare computed and reduced to a single normalised curve, from which the largest possible value of ↑R− for any machine, under any operating conditions, can quickly be assessed for any selected delay in reclosing. The application of this normalised curve is illustrated for three motors not already used, and the results are compared with values obtained from complete-transient solutions.

DOI:10.1049/piee.1969.0369

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Prior to instrumented site tests being carried out on a group of power-station auxiliary motors, computer studies of the site-test conditions were undertaken, and the paper reports the analytical methods developed for the pretest dynamic analyses, together with the correlation achieved between site-test and computed results. For the purposes of the tests, the motors were isolated from the turbogenerator for which they normally function as auxiliaries, and supplied from a neighbouring power station. To assess their recovery to, or divergence from, steady running conditions subsequent to disturbances in the system from which they are supplied, controlled-duration faults were applied at the power station supplying the induction-motor group. In the pretest analyses, 12 subgroups, of a total of 23 motors tested, were independently represented, as was the trubogenerator unit at the neighbouring unit at the neighbouring power station. Central to the analysis is Kron's concept of a synchronously rotating frame of reference, into which the equations of all machines in the group are transformed. It is shown, in the paper, that, after transformation, the machine equations may be arranged in a form particularly suitable for multimachine-system analysis by computer. The overall method of analysis is developed in detail, and its validity is checked by comparisons, made in the paper, of site-test recordings of the principal machine variables, and solutions obtained for them in the pretest computer studies.

DOI:10.1049/piee.1969.0370

出版商:IEE    

年代:1969

数据来源: IET

摘要:

High-voltage power transformers incorporate large quantities of insulation which is easily contaminated, and the dielectric strength is, in consequence, uncertain. This paper reports the results of electric-strength tests on transformer oil, alone and in combination with solid insulation, under various conditions. It is concluded that a major factor determining the maximum local oil stress at failure is the volume of oil under the highest stress, and that, from a knowledge of the failure-stress/volume characteristic for oil in uniform fields, the maximum local oil stress at failure for nonuniform fields can be predicted.

DOI:10.1049/piee.1969.0372

出版商:IEE    

年代:1969

数据来源: IET

摘要:

A recursive differential correction-estimation technique is presented for online estimation of process parameters in the presence of autocorrelated noise. The technique is shown to allow adaptive estimation of changing system parameters. The experimental results of digital simulations indicate that the proposed recursive-estimation algorithm is valuable for online-control applications, and for the estimation of parameters in the presence of large amounts of data by avoiding the need for excessive data storage.

DOI:10.1049/piee.1969.0378

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Pontryagin's method for determining zeros is applied to establish the stability criteria for the 3rd-order retarded system characterised by the normalised transcendental equationH(s, es) =s(s2+ as + b)es+K= 0Various cases are considered in detail. Stability charts based on the stability criteria established are also presented. Critical values of the system parameters obtained from these stability charts agree with the results obtained by the graphical method.

DOI:10.1049/piee.1969.0379

出版商:IEE    

年代:1969

数据来源: IET

摘要:

A method is described for obtaining bounds on the response of 2nd-order nonautonomous systems. The method, which is an extension of the tracking-function method, obtains a closed bounded region in the state plane to which the system trajectories are confined. Originally conceived as a graphical procedure applicable only to autonomous systems, the method is well suited to numerical computation, which both increases its power and facilitates its application. Several examples illustrate the method and show it to be of wider applicability than previous methods.

DOI:10.1049/piee.1969.0380

出版商:IEE    

年代:1969

数据来源: IET

摘要:

Barrett has recently suggested the use of the majorant of a Volterra series for the determination of the system-response bounds. This reduces a nonlinear differential equation to an ordinary algebraic equation, thus considerably facilitating the study of the convergence properties of a Volterra-series expansion. The author has applied this method to a practical problem to investigate the effect of temperature-feedback control on the growth of neutrons in a nuclear-power reactor. This paper determines a sufficient condition for the boundedness of the response of the nuclear reactor subjected to an arbitrary, constantly acting, bounded input. The nonzero initial conditions of the system have been taken into consideration, and their effects on the system response are clearly shown.

DOI:10.1049/piee.1969.0381

出版商:IEE    

年代:1969

数据来源: IET