British Journal of Applied Physics 

About: British Journal of Applied Physics is an academic journal. The journal publishes majorly in the area(s): Cathode & Electron. It has an ISSN identifier of 0508-3443. Over the lifetime, 2589 publications have been published receiving 45427 citations.

The elasticity and strength of paper and other fibrous materials

Abstract: An analysis is made of the effect of orientation of the fibres on the stiffness and strength of paper and other fibrous materials. It is shown that these effects may be represented completely by the first few coefficients of the distribution function for the fibres in respect of orientation, the first three Fourier coefficients for a planar matrix and the first fifteen spherical harmonics for a solid medium. For the planar case it is shown that all possible types of elastic behaviour may be represented by composition of four sets of parallel fibres in appropriate ratios. The means of transfer of load from fibre to fibre are considered and it is concluded that the effect of short fibres may be represented merely by use of a reduced value for their modulus of elasticity. The results of the analysis are applied to certain samples of resin bonded fibrous filled materials and moderately good agreement with experimental results is found.

The viscosity of suspensions of rigid spheres

Abstract: An explanation is given of the dependence of the relative viscosity on the size distribution of the suspended spheres, an effect recently observed by Ward and Whitmore.(1) It is shown theoretically that if the spheres are of very diverse sizes, the relative viscosity is (1 - c)-2.5 for all values of the volume concentration c. For spheres of equal size, the validity of the Einstein expression for the relative viscosity (1 + 2.5c) is restricted to concentrations well below c = 0.05; while for medium and high concentrations the relative viscosity is given by the theoretical expression (1 - 1.35c)-2.5. The use of the latter formula in interpreting measurements on the viscosity of solutions is briefly indicated.

Cerenkov radiation and its applications

Abstract: The paper opens with a brief review of the original discovery of the radiation and the physical principles of the process that gives rise to it. This is followed by an elementary account of the theory of the effect. A general survey of the practical applications to cosmic-ray and high-energy physics is then presented, with two examples of modern detectors discussed in greater detail. The article concludes with an account of recent experiments carried out on light pulses from the night-sky associated with cosmic-ray showers, found to be due to Cerenkov radiation in the atmosphere.

The analysis of grain boundary diffusion measurements

Abstract: Whipple's exact solution of the grain boundary diffusion problem is evaluated numerically and the results presented in graphical form suitable for immediate application to the commoner types of experimental measurement of D?, the grain boundary diffusion coefficient. This enables a detailed comparison to be made between the results obtained using the exact solution and the approximate but commonly employed Fisher solution. The most interesting result is that indiscriminate use of the Fisher equation may lead to anomalously high activation energies for grain boundary diffusion, especially in low angle boundaries. The Whipple solution is also compared with another exact solution due to Suzuoka, which employs a different surface condition from the one assumed by Whipple. For the sectioning method of measurements the two solutions will give nearly the same value of D?. This is a distinct advantage for this method over others, for the conditions prevailing at the surface in a grain boundary experiment are not easily controllable. Mathematical treatments of grain boundary diffusion by other authors are briefly mentioned. Most of these give results already contained in the Whipple solution.

Constriction resistance and the real area of contact

Abstract: The relation between the area of contact and the constriction resistance which holds for a single circular contact spot is widely used in electric contact theory, although the normal mode of contact is by a large number of microcontacts. A method of finding the resistance of a cluster of microcontacts is derived, and it is shown that the resistance may be regarded as the sum of the parallel resistance of the microcontacts and an interaction term often related to the extent of the cluster and not to the number or size of the individual contacts. The resistance is often close to that found by assuming that the entire area covered by the cluster is a single conducting spot. The known agreement between areas of contact found from resistance measurements and by other methods is therefore puzzling - until it is realized that the other methods also give only an apparent area: the real area of contact in, for example, a Brinell indentation is a small fraction of the area of the indentation. Thus from the point of view of electric contact theory the system is self-consistent, although the real area of contact is now seen to play no part in it: the implications for the theory of friction are more profound.