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Showing papers by "Ministry of Supply published in 1950"


Journal ArticleDOI
TL;DR: In this article, the second-harmonic type of magnetic modulator is discussed and a theoretical analysis of an idealized modulator of this type is presented, with particular reference to the influence of various controllable parameters on the signal/noise ratio and zero error.
Abstract: It is well known that certain factors, notably flicker noise and zero drift, determine the smallest signal voltage that can be satisfactorily amplified by a thermionic d.c. amplifier. Better results can often be obtained by using a suitable modulator to convert the direct current to alternating current and following this by an a.c. amplifier and rectifier. The paper discusses the advantages of the second-harmonic type of magnetic modulator for this purpose, and presents a theoretical analysis of an idealized modulator of this type, with particular reference to the influence of various controllable parameters on the signal/noise ratio and zero error. The paper also describes experimental work, which, with allowance for the idealizations in the theoretical analysis, is considered to provide a satisfactory qualitative verification of the latter. Particular emphasis is placed on the need for great care in the design of the various circuits, toeliminate additional sources of noise and zero error, and it is believed that the noise output of the apparatus described is due mainly to Barkhausen effect in the modulator cores, and is equivalent to a signal input of about 10?19 watt for a bandwidth of 1 c/s; the zero drift is, however, considerably greater than this, and is equivalent to a signal input of about 3 × 10?18 watt over a two-hour period.

35 citations


Journal ArticleDOI
R. E. Pattle1
TL;DR: In this article, a large number of substances were tested for ability to destroy the foam on four(different foaming aqueous solutions) and the ability or inability of the anti-foams to spread on the foaming liquid was also studied.
Abstract: A large number of substances were tested for ability to destroy the foam on four(different foaming aqueous solutions. The ability or inability of the anti-foams to spread on the foaming liquid was also studied. It is concluded that anti-foams act by displacing from the surface the substance causing the foaming (or, in salt solutions, preventing negative adsorption). They may do this either by dissolving in the foam liquid or bespreading over its surface.) The causes of the strong, correlation (found) between foam-killing and spreading are discussed.

18 citations



Journal ArticleDOI
TL;DR: The fundamental physical, chemical and mechanical processes which occur when a detonation wave passes through an explosive were imperfectly understood at the beginning of the recent war and many theoretical and experimental studies were made of detonation processes.
Abstract: The fundamental physical, chemical and mechanical processes which occur when a detonation wave passes through an explosive were imperfectly understood at the beginning of the recent war. As part of the scientific war effort in the British Common-wealth and in the United States of America, many theoretical and experimental studies were made of detonation processes. Much of the work has recently been declassified and some has been published. Several centres of research in this country and elsewhere are vigorously continuing with these studies. As later papers will show, the quality and general scientific interest of much of this work was considered sufficient to form the basis of a Discussion of the Royal Society. If one neglects the finite width of the zone in the detonation front where chemical reactions occur, a freely running steady plane detonation front can only advance through an explosive with the Chapman-Jouguet velocity defined by D = u + c . Once the explosive products are formed, their subsequent chemical reactions and motion in the detonation front may be considered as adiabatic. Although Chapman (1899) and Jouguet (1901) correctly stated their equation, neither attempted to discuss the reaction zone itself. It was therefore thought necessary that the recent views on the reaction zone should be described in a manner which throws new light on the Chapman-Jouguet equation. Professor J. von Neumann, Dr⋅ S. F. Boys and Dr A. F. Devonshire were the principal contributors on the theoretical side and von Neumann’s theory (1942) will be outlined later.

12 citations


Journal ArticleDOI
S.S.D. Jones1
TL;DR: In this article, a microwave analogue has been constructed using spaced conducting sheets to produce a region of refractive index varying in accordance with the above relation, which is suitable for wide-angle scanning.
Abstract: For many years it has been known that, in principle, optical lenses could have been made from non-homogeneous glass. For example, if a glass sphere of unit radius were made with refractive index varying according to the relation. ? = ?(2?r2) where ? = refractive index and r = radial distance from centre, it would act as a lens with the focus on the surface of the sphere. Such non-homogeneous glass cannot be produced in practice; however, a microwave analogue has been constructed using spaced conducting sheets to produce a region of refractive index varying in accordance with the above relation. This lens, being circularly symmetrical, is free from aberrations as the feed is moved around the circumference, and is therefore suitable for wide-angle scanning. It will operate only when the direction of polarization is such that the magnetic vector is normal to the conducting sheets.

9 citations


Journal ArticleDOI
01 Dec 1950-Nature
TL;DR: In this article, Kumagai and Isoda showed that the specific burning time is the inverse of a quantity referred to in the work at the National Gas Turbine Establishment as the evaporation constant λ.
Abstract: IT is of interest to find that Drs. Kumagai and Isoda's results are in agreement with the earlier measurements at the National Gas Turbine Establishment. The constant T/d02 they refer to as the specific burning-time is the inverse of a quantity referred to in the work at the National Gas Turbine Establishment as the evaporation constant λ. In the case of liquid fuel drops, the latter concept is perhaps of more general significance, as it can be applied to evaporation under both non-burning and burning conditions. In the low-temperature case the evaporation-rate is determined by diffusion processes, and in the high-temperature case the evaporation-rate is determined by heat transfer processes. In both cases experiments have shown that the mass evaporation-rate is proportional to the first power of the radius of the drop. Hence in both cases T/d02 is constant, and may be conveniently referred to in the general case as the specific lifetime of the drop.

8 citations


Journal ArticleDOI
TL;DR: In this article, the authors used radar sets operating on wavelengths of 9.1, 3.2 and 1.25 cm to investigate the theoretical dependence of radar echo power on drop-size distribution, pulse energy and wavelength.
Abstract: Experiments, using radar sets operating on wavelengths of 9.1, 3.2 and 1.25 cm, are described, the results of which confirm the theoretical dependence of radar echo power on drop-size distribution, pulse energy and wavelength. Measurements of the echo intensity of a "bright band", which appears within echoes from rain at a height a little below the freezing level, are reported, and an explanation of the phenomenon is offered. Some of the uses to which observations of radar echoes from precipitation may be put are mentioned briefly.

8 citations


Journal ArticleDOI
TL;DR: The dose received by backscattering at the front face of a thick layer of scattering material irradiated by a uniform beam of gamma-rays has been evaluated for beam directions between normal incidence and glancing incidence, for gamma-ray energies from 250 keV to 3 MeV as discussed by the authors.
Abstract: The dose received by back-scattering at the front face of a thick layer of scattering material irradiated by a uniform beam of gamma-rays has been evaluated for beam directions between normal incidence and glancing incidence, for gamma-ray energies from 250 keV to 3 MeV. Results are given also for a half-slab, which is useful for building up re-entrant angles by superposition, and for a right-angled corner.

8 citations


Journal ArticleDOI
R. E. Pattle1
TL;DR: In this article, the mechanisms controlling the volume of foam formed by air bubbling continously through a liquid have been studied and the effect of alcohols in enhancing foaming, as well as in destroying foam is noted.
Abstract: The mechanisms controlling the volume of foam formed by air bubbling continously through a liquid have been studied. Examples are given in which one—coalescence of bubbles within the foam— or another—bursting of bubblos at the top of the foam—predominates. The effect of alcohols in enhancing foaming, as well as in destroying foam is noted. The effect of the gm flow rate on foam volume has bed investigated and is found to differs from liquid to liquid. No simple relation between the two exists In the present state of our knowledge the foam volume under-& given circumstances an be found only by experiment.

8 citations


Journal ArticleDOI
TL;DR: The structure of the monoalcohol of 3 : 5-dimethylphenol, first made by von Auwers and believed to be a para-substituted derivative, has now been confirmed.
Abstract: The structure of the monoalcohol of 3 : 5-dimethylphenol, first made by von Auwers and believed to be a para-substituted derivative, has now been confirmed. The synthesis of a new dialcohol, which has been characterized as an ortho-ortho compound, is described. The effect of reaction conditions on the position of methylol substitution is discussed. It has been shown that during characterization of the monoalcohol, by pyrolysis with lime, methyl migration may occur.

7 citations


Journal ArticleDOI
R.F. Proctor1
TL;DR: In this paper, the large increase in the radiation resistance of a horizontal dipole at low heights above the ground, predicted by the mathematical analysis of Sommerfeld and Renner, is confirmed by actual measurement for the case of an essentially pure dielectric ground.
Abstract: The large increase in the radiation resistance of a horizontal dipole at low heights above the ground, predicted by the mathematical analysis of Sommerfeld and Renner, is confirmed by actual measurement for the case of an essentially pure dielectric ground. Measurements carried out above a series of conducting mats of increasing mesh size corroborate the supposition that the large increase in the radiation resistance at low heights is caused by a corresponding increase in the energy radiated downwards into the dielectric ground.

Journal ArticleDOI
J. Brown1
TL;DR: In this paper, it was shown that periodic variations in the field intensity across a radiating aperture may alter the shape of the radiation pattern and reduce the power gain of the aperture, and the way in which such variations arise in the distribution existing across the outer surface of a microwave lens is discussed.
Abstract: Periodic variations in the field intensity across a radiating aperture are investigated, and it is shown that they may alter the shape of the radiation pattern and reduce the power gain of the aperture. The way in which such variations arise in the distribution existing across the outer surface of a microwave lens is discussed.

Journal ArticleDOI
TL;DR: In this article, the authors present a method for the quantitative interpretation of the contours and particular implications of this aspect of micro-photometry, as well as a method to detect trace elements in complex spectra when normal non-recording microphotometry is difficult or impracticable.


Journal ArticleDOI
TL;DR: The accepted structure of this compound was that of a linear molecule of three benzene rings linked by two methylene bridges, and it was later suggested that the compound had a cyclic four-ring structure, but evidence was presented in support of the earlier trinuclear formulation as discussed by the authors.
Abstract: It has been know since 1930 that a compound, m.p. 215° c., can be isolated from a p-cresol-formaldehyde resin made under acid conditions. The accepted structure of this compound was that of a linear molecule of three benzene rings linked by two methylene bridges. It was later suggested that the compound had a cyclic four-ring structure, but evidence is now presented in support of the earlier trinuclear formulation. A new three-ring compound, containing two chlorine atoms in place of two methyl groups, is also described.

Journal ArticleDOI
TL;DR: In this article, plots of water-rate and packing-shape correction factors for four commonly used sizes of Raschig rings to use with a modified Fanning equation are given.
Abstract: Plots of water-rate and packing-shape correction factors for four commonly used sizes of Raschig rings to use with a modified Fanning equation are given. These are for fluid rates commonly associated with distillation, as distinct from absorption. Experimental evidence is given to show the magnitude of the error involved in applying the results obtained with an air/water system to calculations concerning distillation systems.

Journal ArticleDOI
TL;DR: In this article, the case of perpendicular incidence on a plane slab has been studied by various simple theoretical methods, and the best of the simple methods is a modification of the upper limit solution; in problems where this is too difficult to formulate, a good alternative is to calculate the dose from unscattered and once-scattered quanta, giving the latter the penetrating power of the incident quanta and the maximum possible energy-absorption cross-section.
Abstract: As the simplest problem involving the multiple scattering of gamma-rays, the case of perpendicular incidence on a plane slab has been studied by various simple theoretical methods. No exact solution is available as a test of these methods, but approximations of increasing accuracy, known to give too small a dose under the slab, have been combined with a theoretical upper limit for the dose, forming a zone in which the exact solution must lie. Most of the methods tested could be used even if pair-creation or the photoelectric effect gave an appreciable absorption, though for simplicity the computations have been carried out for pure Compton scattering and for quantum energies of a few MeV. Polarization by the Compton effect has been neglected. The best of the simple methods is a modification of the upper limit solution; in problems where this is too difficult to formulate, a good alternative is to calculate the dose from unscattered and once-scattered quanta, giving the latter the penetrating power of the incident quanta and the maximum possible energy-absorption cross-section.

Journal ArticleDOI
TL;DR: In this paper, the effects of air gaps round the source, large source dimensions, and plane absorbing materials on the propagation of gamma-radiation in an extended scattering medium were investigated.
Abstract: Some typical problems of the propagation of gamma-radiation in an extended scattering medium have been solved for pure Compton scattering, which is a good approximation for most materials at gamma-ray energies up to a few MeV. The effects to be expected from air gaps round the source, large source dimensions, and plane absorbing materials are demonstrated.

Journal ArticleDOI
TL;DR: In this paper, the principles underlying the design of the 30-MeV synchrotron are described in relation to general design principles for machines up to 400 MeV, and the mechanism of operation of electron synchrotrons is described.
Abstract: The principles underlying the design of the 30-MeV synchrotron are described in relation to general design principles for machines up to 400 MeV. The mechanism of operation of electron synchrotrons is described, and formulae are derived for specifying design parameters. Some practical points in the design of synchrotron magnets, accelerating chambers and electronic equipment are then considered. Finally, theradiation characteristics of the machines are described. The paper isillustrated by experiments on the 30-MeV A.E.R.E. synchrotron, and by design data on the 375-MeV Glasgow synchrotron.

Journal ArticleDOI
TL;DR: In this article, the authors describe the constructional and electrical features of a 30-MeV synchrotron and compare the performance of two types of magnet types and their performance in terms of magnetic field and acceleration.
Abstract: The paper outlines the constructional and electrical features of a 30-MeV synchrotron. Two types of magnet are described, and theirperformances are compared. Details are given of the accelerating chamber, with its evacuating system, and of the electronic equipment required to control and monitor the machine in operation. The general behaviour is discussed with the help of experimental results. These include the effects of misalignment and disturbance in the magnetic field, gas scattering of the electrons, variations in the injection process, and change in the parameters of the r.f. accelerating field.

Journal ArticleDOI
A. M. Wild1
20 May 1950-Nature
TL;DR: The removal of the procaine ion by precipitation followed by iodimetric determination of the penicillin seemed the most promising line of attack, and Sodium silicomolybdate and sodium silicotungstate were both found suitable for this purpose, although the latter possesses certain advantages over the former and is obtainable commercially.
Abstract: THE iodimetric estimation of procaine penicillin presents difficulties because of the interaction of procaine with iodine. Sodium penicillin to which an equivalent weight of procaine hydrochloride has been added gives results which may be from 3 to 5 per cent lower than for the untreated penicillin. Although the ferricyanide method of Hiscox1 is said to be free from the above objection, we could not obtain consistent results with it, a spread of ± 4 per cent being obtained in a series of determinations on a sample of sodium penicillin. The removal of the procaine ion by precipitation followed by iodimetric determination of the penicillin seemed the most promising line of attack, and sodium silicomolybdate and sodium silicotungstate were both found suitable for this purpose, although the latter possesses certain advantages over the former and is obtainable commercially. Both substances give with procaine salts heavy precipitates which are granular in the presence of sodium chloride (3 per cent) and can readily be centrifuged to a compact mass permitting decantation of the supernatant liquid. Precipitation is virtually complete, and neither precipitant has any action upon iodine or penicillin.

Journal ArticleDOI
R. A. Smith1
21 Jul 1950-Science

Journal ArticleDOI
Phillips G1
03 Jun 1950-Nature
TL;DR: Some quantitative measurements of the surface potential change produced by the deposition of a monomolecular layer of fatty acid on a polished stainless-steel plate are made, particularly at low concentrations, thus extending the earlier work of Frost1,2.
Abstract: IN the course of measuring, in air, the surface potential change produced by the deposition of a monomolecular layer of fatty acid on a polished stainless-steel plate, transient changes of potential were observed, due to the passage over the plate of vapour impurities in the laboratory air. Some quantitative measurements of this effect have been made, particularly at low concentrations, thus extending the earlier work of Frost1,2.

Journal ArticleDOI
TL;DR: In this article, an experimental investigation of the problem of mutual and self-impedance of coupled cylindrical aerials is described, and it is shown that mutual-impingance values, calculated on the assumption that the aerial current distribution is sinusoidal, can be used with some success if appropriate values of self-IMpedance are used.
Abstract: The paper describes an experimental investigation of the problem of mutual and self-impedances of coupled cylindrical aerials. It is shown that mutual-impedance values, calculated on the assumption that the aerial current distribution is sinusoidal, can be used with some success if appropriate values of self-impedance are used. An approximate method for finding these impedances is suggested.


Journal ArticleDOI
TL;DR: In this article, the authors proposed a new conductance standard that should make possible accuracies of better than ± 1 % in conductance and better than 1 μμF in capacitance, depending on the conductance that is being measured at the same time.
Abstract: Transfer standards have been developed for calibrating, at frequencies from 200 kc/s to 60 Mc/s, an admittance bridge which measures 0–100 millimhos and −150 μμF to +150 μμF. The standards have been used to give the bridge accuracies of about ± 2% ± 0.05 millimho in conductance, and between ± 0.2 μμF and ± 4 μμF in capacitance, depending on the conductance that is being measured at the same time. Suggestions are made for a new type of conductance standard that should make possible accuracies of better than ± 1 % in conductance, and better than ± 1 μμF in capacitance.