摘要:

The thermo-electric power of an oxide cathode has been examined recently by J. R. Young, who finds it to be a complex function of temperature, dependent on the dual nature of oxide-cathode conductivity. By an experimental artifice the present authors show that an apparently complex form of behaviour is, in fact, the result of the superposition of two quite simple phenomena. Two parallel-acting thermo-electric power functions are involved, and each of these is invariant with temperature and temperature gradient. The two functions are physically separated and each is measured over an appropriate temperature range. The larger function, of magnitude 2.0 − 3.0mV/degC, is associated with the vacuum movement of electrons through the hollow pores of the oxide matrix; the smaller one, of magnitude 0.5mV/degC, occurs in the chains of contiguous solid particles of the matrix. Owing to the parallel connection and inequality of these functions, it is concluded that a temperature gradient through an oxide matrix leads to a continuous circulation of current, vacuum-wise in one direction and solid-wise in the other. Since the larger function is essentially one involving thermionic emission of electrons in a vacuum, it can be satisfactorily explained in terms of Richardson's law.

DOI:10.1049/pi-c.1961.0013

出版商:IEE    

年代:1961

数据来源: IET

摘要:

Resonance curves of an oscillator with two degrees of freedom and the criteria of stability of the synchronized state are determined theoretically by van der Pol's method of approximation and verified experimentally by an electronic differential analyser. An experimental method for obtaining the phase trajectories is described. Characteristics of oscillations outside the zone of synchronization are also described.

DOI:10.1049/pi-c.1961.0014

出版商:IEE    

年代:1961

数据来源: IET

摘要:

Following a review of nodal analysis of unconstrained lumped linear time-invariant networks it is shown how networks with imposed unilateral constraints, i.e. transmittances and voltage sources, can conveniently be analysed by matrix methods. Their admittance matrix is equal to the product of a submatrix of the admittance matrix before the application of the constraints and a transmittance matrix which describes the constraints. Constraints lower the rank of the original admittance matrix, thus making the method quite attractive in practice. Applications included are a computing network, difference amplifiers, a d.c. amplifier and signal-flow graphs.

DOI:10.1049/pi-c.1961.0015

出版商:IEE    

年代:1961

数据来源: IET

摘要:

A procedure is described for the design of wide-band bandpass amplifiers using either stagger-tuned stages or a chain of feedback pairs to realize Cheby̅shev or Butterworth response shapes.A graphical test has been developed by which it is possible to verify, at the outset, that a given design specification is a realizable one. Certain fundamental limitations which are imposed upon the response shapes by the choice of these circuit configurations are revealed by this test. Thus it is shown that any response shape which may be realized by a chain of feedback pairs can also be realized with stagger-tuned stages, while the converse is not true.An example demonstrating the application of the procedure to a design problem has been included to demonstrate that the procedure for a Cheby̅shev response is no more complicated than for a Butterworth response, neither is any additional complication introduced by increasing the number of singularities in the desired response shape beyond the first pair, since each pair of singularities is separately realized.

DOI:10.1049/pi-c.1961.0016

出版商:IEE    

年代:1961

数据来源: IET

摘要:

It is shown that the multi-gain representation for a single-valued non-linearity with multiple inputs as developed by Somerville and Atherton may be regarded as an approximation problem involving orthogonal polynomials in two variables.Consider two stationary random processes,x(t)andy(t), possibly correlated, with a given second-order (zero-delay) joint probability density,p(x,y). If the input to a specified zero-memory non-linear device having the input/output characteristicv0(t)=f[vi(t)]isx(t)+y(t), the relevant polynomials satisfy orthonormality conditions over the xy-plane with respect top(x, y)as weighting function. An inherent minimum property of these polynomials then allows the equivalent gains to be determined directly in terms of the expansion coefficients off(x+y)with respect to the polynomials. Whenxandyare uncorrelated, the gains reduce to the values previously obtained by Somerville and Atherton.A further property of the polynomials is sufficient to prove that the zero-delay cross-correlation between the input and the error involved in the approximation is zero, and that this result remains true as the order of the approximation is increased.

DOI:10.1049/pi-c.1961.0017

出版商:IEE    

年代:1961

数据来源: IET

摘要:

A perturbation analysis is used to demonstrate the instability of a type of electron flow in a plane diode known as C-overlap flow, which is predicted to be a possible flow in the approximation in which electrons are emitted from the cathode with a uniform velocity.

DOI:10.1049/pi-c.1961.0018

出版商:IEE    

年代:1961

数据来源: IET

摘要:

Generally an electrical network is used as a model circuit for a physical field. This circuit is most complicated and the analysis of it is frequently difficult. ‘Diakoptics’, introduced by Kron, is very effective for analysis of the network. The method entails the operation of ‘cutting’, which is generally classified into open-circuiting and short-circuiting. The latter operation is the dual of the former, but, as far as the author is aware, has not yet been reported in any of the literature. A method is described, based on Kron's diakoptics, which uses the operation of open-circuiting, and is further extended to dual diakoptics treated by the operation of short-circuiting. Here a simplification of Kron's diakoptics is attempted and a dual method is introduced. It seems that this attempt goes backwards in tensor geometry, but forward in combinatorial topology. The first intention of the paper is to show the duality between diakoptics and codiakoptics.

DOI:10.1049/pi-c.1961.0019

出版商:IEE    

年代:1961

数据来源: IET

摘要:

A recent re-examination of the phenomenon of tooth-ripple flux pulsations at laminated pole-faces in alternators resulted in a new theoretical analysis by means of which the pole-face eddy-current loss can be calculated. The primary purpose of the present investigation has been to make measurements of tooth-ripple losses which could be compared with values calculated from the new formulae. In order to make these measurements an experimental homopolar machine was built and values of eddy-current losses were determined over a fairly wide range of flux density and frequency for four different thicknesses of lamination. It is found that there is moderately good agreement between calculation and experiment for the thicker laminations and in general the agreement is markedly better with the new formulae than with those previously developed.

DOI:10.1049/pi-c.1961.0020

出版商:IEE    

年代:1961

数据来源: IET

摘要:

An audio signal may be decomposed into components having certain frequency and phase. Half the information of the signal is contained in the phase of the frequency components. Since the human ear is almost insensitive to phase, one may eliminate the phase information without causing a noticeable reduction in the signal quality. The elimination of the phase information implies a permissible reduction of the bandwidth required for the transmission of the signal to one-half and a reduction of the signal power by 3 dB without increase of distortions due to additive white normal noise. A method for the elimination of the phase information is based on the decomposition of the audio signal by correlation with a set of orthogonal functions. These correlations yield for each orthogonal function one coefficient which is represented by a voltage. One may process these coefficients in analogue or digital computers to reduce further the bandwidth required for the transmission of audio signals with certain spectral distribution, e. g. voice signals.

DOI:10.1049/pi-c.1961.0021

出版商:IEE    

年代:1961

数据来源: IET

摘要:

The paper reviews the practicability of setting up physically, in the form of specialized networks, several of the equivalent circuits representing an unbalanced 2-phase induction motor. This motor sufficiently general to include, as special cases, most induction machines with balanced secondary windings.

DOI:10.1049/pi-c.1961.0022

出版商:IEE    

年代:1961

数据来源: IET