Showing papers by "Ministry of Supply published in 1951"

The Coagulation and Deposition of a Stirred Aerosol

Abstract: Langstroth and Gillespie have determined experimentally the rate of change of particle number in ammonium chloride smokes in still and moving air, and have analysed their results into deposition on the walls and coagulation inside the aerosol cloud It is shown here that the empirical constants describing these processes can be explained on theoretical grounds, both in order of magnitude and as regards their variation with the rate of stirring

Inormation Theory and the Design of Radar Receivers

Abstract: The paper deals with the problem, frequently encountered in radar, of extracting simple numerical information from a noisy waveform. It is suggested that the only ideal way of doing this is to use the principle of inverse probability and convert the wave-form into a probability distribution for the quantity sought. The method is applied to the problem of determining the time delay of a periodically modulated rf waveform in the presence of white Gaussian noise when the undelayed waveform without noise is exactly known. As a result, the matched predetection filter of Van Vleck and Middleton is automatically specified, and the theory of ideal detection is briefly indicated.

A Note on the Pseudo-Stationary Flow behind a Strong Shock Diffracted or Reflected at a Corner

Abstract: It is shown that the equations of an unsteady compressible flow in the ( x, y )-plane, which is expressible in terms of the two variables x/t and y/t only, can be reduced to those of a steady compressible flow with a non-conservative field of external forces and a field of sinks. The steady-flow problems of this type, which correspond to the diffraction or reflexion of a plane shock travelling parallel to a rigid wall and reaching a corner, are discussed qualitatively. It is shown that, under certain conditions, there are regions in the corresponding steady flows which are entirely supersonic and for which a simple solution can be given without determining the whole field of flow. No complete solution for the whole field of flow has yet been given. In the diffraction, at a convex corner, of certain strong shocks, it is shown that there can be an area of Prandtl-Meyer flow, uniformly increasing with time, and that the upper limit to which it can extend is calculable as a characteristic curve in the corresponding steady flow. In the case of regular reflexion beyond a concave comer, or reflexion at a concave corner which gives rise to a reflected shock passing through the corner, it is shown that there can be areas of uniform flow, uniformly increasing with time, and that the upper limits to which they can extend are arcs of circles, which appear as sonic curves in the corresponding steady flows.

Sorption of solid insecticides by dried mud.

Abstract: IN the course of experiments on the persistence of deposits from aqueous suspensions of different particle sizes of volatile insecticides, it has been found that the residual toxicity of particles of any one size is influenced considerably by the type of material to which they are applied.

An electronic method of detecting impurities in the air

Abstract: Impurity concentrations in clean dry air of one part in 107 by weight of polar vapours or of one part in 104 by weight of non-polar vapours were measured in terms of changes in surface potential of a prepared plate. Changes of potential of the order of 10 μV were measured using a vibrating condenser technique and a selective phase-sensitive amplifier. The results suggest that whilst the adsorption is caused mainly by electrostatic attraction between the dipole and its induced image, a small contribution is also caused by van der Waals attractive forces. The possibilities of obtaining selective adsorption, and some of the practical applications are discussed briefly.

Formaldehyde condensations with phenol and its homologues. XII. The dehalogenation of halogenated diphenylmethanes having halogen substituents in the nucleus

Abstract: The preparation of I-hydroxy-2 : 6-bis-(2-hydroxybenzyl)benzene by dehalogenation of the corresponding trichloro compound was described in Part X of this series (Finn, Lewis & Megson, 1950). The removal of the chlorine was effected by treatment of the boiling amyl alcohol solution of the compound with sodium. The yield was poor and amounted to only 5% of theory. It has now been found that the dehalogenation can be achieved more satisfactorily by treatment of a solution of the diphenylmethane derivative in aqueous sodium hydroxide with Raney nickel-aluminium alloy. A yield of about 50% of theory is obtained. 2 : 2′-Dihydroxydiphenylmethane may be obtained from 2 : 2′-dihydroxy-5 : 5′-dichloro-diphenylmethane by the same means and the method has been used to prepare 2 : 2′-dihydroxy-3 : 5-dimethyldiphenylmethane, 2 : 2′-dihydroxy-3 : 3′ : 5 : 5′-tetramethyldiphenylmethane, and I-hydroxy-3 : 5-dimethyl-2 : 6-bis-(2-hydroxybenzyl)benzene.

Time-delays in low voltage halogen quenched Geiger-Müller counters.

Abstract: LOW-VOLTAGE halogen-quenched Geiger–Muller counters find increasing applications in many fields, especially for use in portable survey and assay instruments1. Their chief advantages are: (i) very low temperature coefficient down to – 50° C.; (ii) very long counting life; (iii) extreme electrical robustness; (iv) simple battery requirements; (v) large output pulse necessitating no pre-amplification.

A survey of quality and reliability standards in electronic valves for service equipment

Abstract: The paper describes the factors which are involved in the use of electronic valves in Service equipment at the present time and the underlying principles which are involved in the procedure and methods adopted to obtain the supply of satisfactory valves. It discusses the widening of the field of application of the electronic valve, the growing complexity of modern Service equipment and the conditions of shock and vibration which have to be withstood. The need for greater reliability is examined and an indication given of the very low failure rate which it is necessary to achieve.

The New Factory

Abstract: The building of a new factory is a major project, and the co-ordination of all interests, mechanical, civil, electrical, and administrative, connected therewith forms the subject of the paper.Special attention is drawn to the appointment of the project manager, his terms of reference, his authority, and his responsibility, upon which is based the organization for co-ordination. Stress is laid on the personal attitude of all concerned, who must sink personal feelings, jealousies, or bias, in favour of the satisfactory conclusion of the project.A broad plan, prepared by the permanent staff of the company should give as much information as possible to the project manager, who preferably will not be a permanent member of the staff himself. The project manager and his committee will formulate the final plan, and carry the project through to conclusion, but not finality.Time spent on the site selection is time well spent, since the site is permanent. Attention must be paid to position, labour, foundations, proc...

A contribution to the algebra of relay and switch contacts

Abstract: The paper is complementary to a paper by G.A. Montgomerie and it suggests that the method of algebraic manipulation proposed by Montgomerie may be considerably improved. In Montgomerie's paper, a closed contact is allotted the symbol unity, and an open ontact the symbol zero. Contacts in series are then treated as if additive, while contacts in parallel are treated as if multiplicative.The present paper shows that, if contacts in series are treated as multiplicative and contacts in parallel as additive, a considerable simplification of algebra results, with a concomitant gain in elegance. This usage avoids the necessity for rules such as 1+0 = 0, 1×0 = 1, which are in direct conflict with those of ordinary algebra. Also, many results which according to the original proposal would be obtained only after considerable manipulation are obtainable at sightusing the methods now proposed.

Corrosion experiments with gaseous boron trifluoride

Abstract: A number of constructional materials—metals, alloys and miscellaneous compounds—which may be required to come into contact with boron trifluoride were subjected to treatment with this gas under carefully controlled conditions. The materials were examined by bringing into contact with gas at an original fixed pressure of about 25 cm. of mercury, and at temperatures up to 200° c. The extent of the reaction, if any, was shown by the alteration of the gas pressure over the sample. Many of the materials examined showed a high resistance to chemical attack by boron trifluoride. The following materials can be safely used in apparatus for handling dry boron trifluoride : stainless steel, mild steel, copper, nickel, Monel metal, brass and aluminium, the more noble metals up to at least 200° c.; Pyrex glass is also suitable up to about 200° c.; Araldite cement, fired pyrophyllite and polytetrafluoroethylene may be used up to 80° c. Great variation was shown by the others in the miscellaneous group of compounds.

A sensitive method of recording nuclear induction signals.

Abstract: IN the detection of nuclear induction signals, it is usual to modulate the main polarizing magnetic field in such a way that its intensity sweeps cyclically over a small region embracing the resonance value1. If the amplified signal is fed to a cathode-ray oscilloscope in which the X-sweep follows the instantaneous field modulation, it gives rise to a ‘blip’ at a corresponding part of the trace.

A modified method for the determination of total penicillin in procaine penicillin

Abstract: A method is described for the chemical assay of total penicillin (salt) in procaine penicillin [penicillin (procaine salt)] The method depends on the conversion of procaine penicillin to sodium penicillin [penicillin (sodium salt)] by precipitation with sodium silicotungstate, the sodium penicillin being assayed iodimetrically

Design of packed distillation columns. IV. An empirical method for the estimation of column height using the H.E.T.P. concept

Abstract: Published results on packed columns and some additional original data on semi-technical columns filled with Raschig rings are presented in a form permitting correlation of H.E.T.P. values with packing diameter, rate of liquid flow and liquid viscosity.