Showing papers in "Philosophical Magazine Series 1 in 1954"
TL;DR: In this paper, the elastic and plastic properties of pure polycrystalline metals are discussed and a systematic relation between shear modulus, Burgers vector and plastic shear strength of metals possessing the same lattice structure is proposed.
Abstract: Relations between the elastic and plastic properties of pure polycrystalline metals are discussed and a systematic relation between shear modulus, Burgers vector and plastic shear strength of metals possessing the same lattice structure is proposed. In addition reasons are given for believing that in a limited temperature range malleability is related to Poisson's ratio.
5,719 citations
TL;DR: In this article, a simplified model for studying grain boundary diffusion of one metal into another was proposed, which has obvious application to the study of heat flow in a poorly conducting solid with a metallic fin.
Abstract: Formulae are obtained for the concentration in a poorly diffusing half space bisected by a thin well-diffusing slab, at different times after the edge of the half-space has been suddenly raised from zero to unit concentration. This represents a simplified model for studying ‘grain boundary’ diffusion of one metal into another. The problem also has obvious application to the study of heat flow in a poorly conducting solid with a metallic fin.
610 citations
Abstract: Summary A new type of interferometer for measuring the diameter of discrete radio sources is described and its mathematical theory is given. The principle of the instrument is based upon the correlation between the rectified outputs of two independent receivers at each end of a baseline, and it is shown that the cross-correlation coefficient between these outputs is proportional to the square of the amplitude of the Fourier transform of the intensity distribution across the source. The analysis shows that it should be possible to operate the new instrument with extremely long baselines and that it should be almost unaffected by ionospheric irregularities.
514 citations
TL;DR: In this paper, a simple model was proposed to identify dislocation acceptors with dangling unpaired electrons on the edge of the extra atomic plane of a dislocation having some edge component.
Abstract: Dislocations have a large effect on the electrical properties of germanium. Experiments show that dislocations act as acceptor centres. This paper discusses a simple model (due to W. Shockley) which identifies dislocation acceptors with the dangling unpaired electrons on the edge of the extra atomic plane of a dislocation having some edge component. In n-type germanium the line of acceptors along a dislocation accepts electrons and becomes negatively charged. The electrostatic energy in the resulting space charge region is found and shown to be a dominant factor in determining the occupation of dislocation acceptors. Formulas are given for the temperature variation of the average electron concentration in n-type material that has been lightly deformed by plastic bending. Experiments are suggested to test the theory and determine exactly the energy level of the dislocation acceptors.
391 citations
157 citations
TL;DR: In this article, the authors investigated the disturbance produced behind a shock wave of arbitrary strength, travelling along a tube of varying cross section, and found that the pressure is affected by two distinct perturbations superimposed on the initial flow, namely a permanent modification arising directly from the variations in cross section and a transient disturbance reflected from the shock and propagated with sonic velocity relative to the main flow.
Abstract: Summary The disturbance produced behind a shock wave of arbitrary strength, travelling along a tube of varying cross section, is investigated. The shape of the cross section is arbitrary and the problem is linearized on the basis of small variations in area along the length of the tube. It is found that if the initial cross sectional area is S, and there is a net change in area of amount [AN], then the consequent change in pressure behind the shock is where (p 1−p 0) is the initial pressure discontinuity across the shock. The parameter K decreases monotonically with the shock strength and 0·5⩾K>0·394. More generally it is shown that the pressure is affected by two distinct perturbations superimposed on the initial flow, namely a permanent modification arising directly from the variations in cross section, and a transient disturbance reflected from the shock and propagated with sonic velocity relative to the main flow. Expressions for both these contributions are obtained.
148 citations
TL;DR: From the observed momenta and angles of decays in flight, variables are constructed which are better suited for the analysis than the measured quantities themselves as discussed by the authors, and the regularities in the distribution of the new variables, to be expected from a two-body decay, are discussed.
Abstract: From the observed momenta and angles of decays in flight, variables are constructed which are better suited for the analysis than the measured quantities themselves. These variables are 1/P, the reciprocal of the primary momentum, α, a combination of the longitudinal momenta of the secondaries, and either pt , the transverse momentum, or the quantity e=2pt/P. The regularities in the distribution of the new variables, to be expected from a two-body decay, are discussed. The decay scheme may be derived by comparison with the experimental distributions.
109 citations
TL;DR: In this article, a survey was carried out to measure the natural remanent magnetism of Triassic sediments in England, and the results showed that approximately half of the specimens showed reverse polarization.
Abstract: This paper describes a survey which was carried out to measure the natural remanent magnetism of Triassic sediments in England. Rocks from nine separate sites distributed over a wide area were found to have consistent polarizations, being magnetized in an approximately North East-South Westerly direction with dips significantly less than that of the present earth's field. Similar results were obtained for sediments of the Carboniferous and Old Red Sandstone periods taken from two other sites. Approximately half of the specimens showed reverse polarization. Tests were also made to measure the magnetic stability of the rocks. The possible implications of the results are discussed.
97 citations
TL;DR: In this article, a sequel to a previous one (Read 1954) dealing with the acceptor centres associated with dislocations in germanium is presented, where several approximations are compared by plotting the fraction of acceptors that are full vs. temperature for a particular example.
Abstract: This paper is a sequel to a previous one (Read 1954) dealing with the acceptor centres associated with dislocations in germanium. The previous paper developed two approximations for the statistics of occupation of dislocation acceptors. This paper presents some further approximations that take account of the non-uniform spacing of accepted electrons along the dislocation. It also treats the case where the dislocation acceptors have a range of energy levels (rather than a single level). The several approximations are compared by plotting the fraction of acceptors that are full vs. temperature for a particular example.
88 citations
TL;DR: In this paper, a theoretical treatment for calculating the heats of formation of binary alloys for any composition is put forward, based upon the assumption that the free electrons in a binary alloy exist in two sets of energy levels associated with the potential fields of the ions of the two elements in the alloy.
Abstract: A theoretical treatment for calculating the heats of formation of binary alloys for any composition is put forward. The model is based upon the assumption that the free electrons in a binary alloy exist in two sets of energy levels associated with the potential fields of the ions of the two elements in the alloy. This assumption is a natural consequence of neglecting the changes in the Wigner-Seitz boundary conditions, imposed upon the electrons in the pure elements, when the atoms are randomly mixed in an alloy. Fair agreement between calculated and experimental heats of formation is obtained for many systems, in which the two elements composing a given system are not too far removed from one another in the periodic classification of the elements.
66 citations
TL;DR: In this article, the L and M bands of the Fe group metals were compared with new work by Cauchois and Gyorgy and Harvey and a number of differences are discussed.
Abstract: The paper describes some old unpublished work on the L and M bands of the Fe group metals, and compares the results with new work by Cauchois and Gyorgy and Harvey. A number of differences are discussed. Our results support Farineau's old curves for Cu as against Cauchois', and we are unable to find evidence for the sharp M-emission edges found by Gyorgy and Harvey. Some comment is also given about various suggestions on the general interpretation of soft x-ray levels.
TL;DR: In this paper, the authors derived expressions for the average elastic constants of a poly-crystalline bar, having circular symmetry about its principal axis, and composed of material with cubic crystal symmetry, and showed that the differences between these and the corresponding constants obtained for a material with completely random orientation depend in each case on the same function of the crystal orientation distribution.
Abstract: Summary Expressions are derived for the average elastic constants of a poly-crystalline bar, having circular symmetry about its principal axis, and composed of material with cubic crystal symmetry. It is shown that the differences between these and the corresponding constants obtained for a material with completely random orientation depend in each case on the same function of the crystal orientation distribution, and therefore the complete elastic behaviour of the material may be determined from measurements of three independent quantities. In particular, it is shown how the true elastic constants of an isotropic specimen may be determined from the results of a series of longitudinal and torsional resonance tests, or from three measurements of travel-time of high-frequency pulses of mechanical energy through the material. When the orientation distribution is expressed in terms of zonal harmonics it is found that elastic anisotropy is caused solely by the presence of the component P 4 (cos θ). Stereograph...
TL;DR: In this paper, a method for the systematic measurement of winds at altitudes of 80-100 km is described, where wind drifts of ionized meteor trails cause small changes in range of the radio echoes, and these are measured using a coherent pulse doppler technique.
Abstract: A method for the systematic measurement of winds at altitudes of 80–100 km is described. Wind drifts of ionized meteor trails cause small changes in range of the radio echoes, and these are measured using a coherent pulse doppler technique. The method is able to resolve mean hourly wind speeds and directions on any day. Observations during September and October 1953, have shown that both semi-diurnal and diurnal wind components exist, corresponding to clockwise rotations of the wind vectors. The amplitudes and phases of these components are variable. There is also a prevailing wind which blows towards the east in September, and towards the west in October. The presence of a positive wind gradient of approximately 2·7 m sec-1 km-1 between altitudes of 78 and 98 km has also been established.
TL;DR: The specific heat of solid hydrogen has been measured as a function of the ortho/para concentration in the temperature range from 1·15°k to the triple point as discussed by the authors.
Abstract: The specific heat of solid hydrogen has been measured as a function of the ortho/para concentration in the temperature range from 1·15°k to the triple point. It has been shown that the specific heat contribution of the ortho molecules is anomalous throughout this region, and that the anomaly assumes a cooperative character at the lowest temperatures for specimens rich in orthohydrogen. The temperature of the maximum of the cooperative anomaly is at 1·6°k in normal hydrogen, but shifts rather rapidly to lower temperatures with falling orthohydrogen concentration. Considerations of the entropy show that the entire anomalous behaviour can be associated with the ordering of the rotations of the ortho molecules.
TL;DR: The spectral lines of B-stars belonging to the Orion Nebula group, relative to the lines of the spectrum of the Nebula itself, are shown to be about ten times larger than the red shift which the theory of relativity predicts on the basis of the known values of their masses and radii as discussed by the authors.
Abstract: The red shift of the spectral lines of B-stars belonging to the Orion Nebula group, relative to the lines of the spectrum of the Nebula itself, is shown to be about ten times larger than the red shift which the theory of relativity predicts on the basis of the known values of their masses and radii. A similar discrepancy is found in the case of O-stars. It is suggested that the red shift may be due to a loss of energy in the radiation field of the star. If Δ v is the change of frequency of the line and v its original frequency, the following formula is proposed. when A is a constant, T the temperature of the radiation field and l the length of path traversed through the radiation field.
TL;DR: In this article, the Simon melting equation pm /a=(Tm /T 0)c-1 is derived assuming the validity of the Gruneisen equation of state and the Lindemann melting formula along the melting line.
Abstract: The Simon melting equation pm /a=(Tm /T 0)c-1 is derived assuming the validity of the Gruneisen equation of state and the Lindemann melting formula along the melting line. A relation between c and Gruneisen's γ is derived and discussed in view of available experimental data. Poor agreement is found in the case of the alkali metals, the agreement for argon being satisfactory. A consequence of possible geophysical interest arising from the theory is discussed. The detailed data available for solid helium are used to study the assumptions underlying the theory.
TL;DR: In this paper, the authors used electrical resistance as an indicator for ordering and found that Cu3Au specimens prepared in a state of long-range order and then water quenched from 380°c (8°c below the critical temperature) show an ordering effect at about 100°c.
Abstract: Summary Using the electrical resistance as an indicator for ordering it is found that Cu3Au specimens prepared in a state of long-range order and then water quenched from 380°c (8°c below the critical temperature) show an ordering effect at about 100°c. After this has decayed a similar effect is again observed after an electron bombardment (energies of 0·5 and 1 mev) or after a small deformation at room temperature. An activation energy E∼0·9 ev for all three cases is determined. Attributing the ordering effect to the migration of vacancies or interstitials the experiments provide evidence that one of both of these defects are obtained in thermodynamic excess by quenching or deforming.
TL;DR: In this paper, the authors described laboratory experiments in which air is blown over a viscous oil in a wind tunnel and the aerodynamic drag on the oil surface was also measured, and it appears that once the critical windspeed has been exceeded, the oil acts rather similarly to water, so far as drag forces are concerned.
Abstract: Summary Laboratory experiments are described in which air is blown over a viscous oil in a wind tunnel. At low windspeeds no waves at all appear on the surface, but at a sharply denned critical windspeed small ripples appear, some of which are unstable and grow quickly. The phenomenon is thought to be the instability predicted by Kelvin, which is not observed clearly on the sea. The sort of waves which grow by Jeffreys' ‘sheltering’ process do not appear until a higher windspeed than the critical one. The aerodynamic drag on the oil surface was also measured, and it appears that once the critical windspeed has been exceeded, the oil acts rather similarly to water, so far as drag forces are concerned.
TL;DR: In this paper, the authors derived expressions for the elastic stresses round a long straight crack of constant form moving in an isotropic elastic medium under a general state of applied stress, and examined the mechanical twinning to be expected on the cleavage surfaces of single crystals, on the assumption that this twinning is initiated by the high local stresses near the propagating fracture crack.
Abstract: Summary Expressions are derived for the elastic stresses round a long straight crack of constant form moving in an isotropic elastic medium under a general state of applied stress. These are used to examine the mechanical twinning to be expected on the cleavage surfaces of single crystals, on the assumption that this twinning is initiated by the high local stresses near the propagating fracture crack. It is assumed that the twin formation is controlled by the value of the local shear stress on the twinning plane resolved in the twinning direction. The theory is applied in detail to the twinning and certain other features of the deformation associated with the cleavage fracture of zinc single crystals. It provides a consistent explanation of some experimental observations reported in an accompanying paper by Deruyttere and Greenough. Applications of the analysis to other materials, and to other inhomogeneities causing high local stresses are also discussed.
TL;DR: In this article, the dependence of yield stress on the size of ordered domains has been investigated by tensile deformation of polycrystalline wires of Cu3Au, and it was found that the yield stress was greatest when the estimated domain size was about 50 A.
Abstract: The dependence of yield stress on the size of ordered domains has been investigated by tensile deformation of polycrystalline wires of Cu3Au. In agreement with a prediction by Cottrell it was found that the yield stress was greatest when the estimated domain size was about 50 A.
TL;DR: In this paper, sixteen Geiger counters each of area 200 cm2 arranged on a square lattice of 54 m pitch were used in coincidence to count showers of energies about 1016, 2×1016, 5×1016 and 1017 ev.
Abstract: An experiment is described in which sixteen Geiger counters each of area 200 cm2 arranged on a square lattice of 54 m pitch were used in coincidence to count showers of energies about 1016, 2×1016, 5×1016 and 1017 ev. From the shower rates, no evidence of a deviation from the power law spectrum, R(>E) ∝ E -1·7, was found. The results are analysed in solar and sidereal time. In solar time no variations greater than 1% for the 1016 ev showers or 10% for the 1017 ev showers were found, and these amplitudes could easily arise as a result of statistical fluctuations. In sidereal time, no variation greater than 0·6% was observed at an energy of 1016 ev. At 2×1016 and 5×10 16 ev, small variations were observed which had about 1% chance of being due to random fluctuations. The bearing of these results on theories of the origin of cosmic rays is discussed.
TL;DR: The physical mechanisms of the various processes which may occur as a result of encounters between low velocity atoms or ions are discussed in this article, with particular attention being paid to the factors which determine whether or not a collision is likely to be near-adiabatic.
Abstract: The physical mechanisms of the various processes which may occur as a result of encounters between low velocity atoms or ions are discussed, particular attention being paid to the factors which determine whether or not a collision is likely to be near-adiabatic. The following are the processes considered :
TL;DR: In this article, the β-spectrum of the decay of naturally occurring 178Lu was studied in detail using a well-shielded proportional tube spectrometer and a half-life of 4·56 ± 0·3 × 1010 years was obtained for the γ-transition with a maximum energy of 425±15 kev and the log ft value, 18·75, suggests a 3rd or 4th forbidden transition.
Abstract: The radiations from the decay of naturally occurring 178Lu are studied in detail. The β --spectrum, which was found to be of allowed shape, was investigated using internally mounted sources of thickness 0·149 mg/cm2 and 0·149 mg/cm2 in a well-shielded proportional tube spectrometer. A half-life of 4·56 ±0·3 × 1010 years was obtained for the β-transition with a maximum energy of 425±15 kev and the log ft value, 18·75, suggests a 3rd or 4th forbidden transition. Strong electron peaks arising from the internal conversion of an 89kev γ-ray were observed and a K-capture branching ratio of 3 ± 1 % is derived from a study of the intensity and nature of the L x-rays accompanying the disintegrations. NaI scintillation counters were used for the measurement of γ-rays of energy 3l0 ± 10 kev and 190 ± 10 kev and the evaluation of their internal conversion coefficients classifies them as E.Q. transitions. The intensities of the γ-quanta and the occurrence of γ-γ coincidences conclusively establish the decay s...
TL;DR: The Paramagnetic Resonance in activated carbon has been studied in this paper, where it has been shown that it can be used to detect the presence of paramagnetic resonance in carbon.
Abstract: (1954). Paramagnetic resonance in activated carbon. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 45, No. 364, pp. 545-547.
TL;DR: In a stack of stripped photographic emulsions, twenty events of type 2+0 n have been observed, in each of which the outgoing particles are a proton and a negative π-meson respectively; the latter particle was identified by the characteristic star it produced when brought to rest in the emulsion.
Abstract: Summary In a stack of stripped photographic emulsions, twenty events of type 2+0 n have been observed, in each of which the outgoing particles are a proton and a negative π-meson respectively; the latter particle was identified by the characteristic star it produced when brought to rest in the emulsion. Assuming that each of these events represents the decay in flight of a neutral hyperon according to the scheme Λ 0→π -+P+Q, values of the energy release Q have been calculated. In eleven of the events the proton could be traced to the end of its range; the energies of both particles could then be deduced using appropriate range-energy relations. In the remaining nine examples, the energy of the proton was deduced from grain density considerations and was accordingly less well determined.
TL;DR: The half-lives, mass assignments and radiation characteristics of the neutron excess iridium isotopes have been determined as follows: The gamma-ray energies of 19-hour 194mIr have also been examined.
Abstract: The half-lives, mass assignments and radiation characteristics of the neutron excess iridium isotopes have been determined as follows: The gamma-ray energies of 19-hour 194Ir have also been examined. The 7-second 194mIr isomer is either a 125 kev E3 transition followed by the 5·6 mev gamma-ray or possibly a 5·6mev M6, E6 or E7 transition followed by a 125 kev M1. E2 or E3 gamma-ray. The latter alternative would be the highest spin-change gamma decaying isomer yet discovered and both are unusual in the very high energy transition involved.
TL;DR: In this article, it was shown that the effective wavelength of the ionospheric irregularities remains appreciably constant over a velocity range of 20 : 1, so that the magnitude of the drift velocity may be estimated from a count of the fading rate.
Abstract: Summary The metre wavelength emission from the radio stars is diffracted by irregularities in the electron density of the ionosphere, which occur mainly at night at a height of approximately 400 km. Fading records taken with three receiving equipments, triangularly sited, show systematic time displacements, and these are attributed to a steady translational movement of the diffracting screen. The motion is normally of the order of 50—300 m/sec, is generally transverse to the magnetic lines of force and often remains constant over periods of many hours. During the first half of the night the prevailing direction is towards the West, at approximately 01h there is often a reversal, normally effected within a period of 30 minutes, and thereafter the motions are predominantly towards the East. The effective wavelength of the ionospheric irregularities remains appreciably constant over a velocity range of 20 : 1, so that the magnitude of the drift velocity may be estimated from a count of the fading rate. By ob...