Journal of Physics D: Applied Physics

Kendall, K

doi: 10.1088/0022-3727/17/10/001pmid: N/A

There is an error in the standard fracture mechanics of bent beams. This error is significant for highly deflected beams containing short cracks, such as aircraft wings, and may cause the bending strength to be overestimated by 56% in the worst case. In this letter a new theory of bending failure explains this error and shows that the strength of a bent beam decreases as the span is increased, in good agreement with experimental results.

Singh, R

doi: 10.1088/0022-3727/17/10/003pmid: N/A

Temperature dependence of electron spin resonance (ESR) in as-cast and heat-treated samples of 35TeO2-(65-x)V2O5-xFe2O3 (mol.%) glasses was studied. V4+-Fe3+ and Fe3+-Fe3+ pairs exist in these glasses. The authors have observed for the first time a phenomenon of 'vanishing' magnetism in the heat-treated samples of these glasses containing Fe2O3 between 1 and 5 mol.%. This phenomenon occurs above 250K and it is due to the phonon-induced superexchange interactions between 3d transition metal ions in V4+-O-Fe3+ and Fe3+-O-Fe3+ bonds.

Hemmes, K; Lodder, J C; Rekveldt, M Th; Kraan, W H

doi: 10.1088/0022-3727/17/10/002pmid: N/A

The domain structure of relatively thick RF-sputtered CoCr (81:19 at.%) layers with a columnar morphology in the range of thickness 1-5 mu m was investigated using a polarised neutron beam. On the basis of the results a model of straight domains running through the entire film thickness has to be rejected. Arguments are given for a serpentine-like domain structure with a domain width about the same as the column diameter (0.1-0.3 mu m), resulting in a 'chain of columns' model.

Adrain, R S; Watson, J

doi: 10.1088/0022-3727/17/10/004pmid: N/A

In the twenty years of so since its inception, 'laser microspectral analysis' (LMSA) has become an established technique for rapid, spot analysis of solid targets. Since a laser is used to vaporise the sample, little or no preparation is required and analysis of dielectric and conducting samples can be performed. Only microgram quantities of about 50 mu m diameter are sampled and, as such, the technique fills the gap between electron and ion microprobes and conventional emission spectroscopy. The authors discuss the physical characteristics of laser produced plasmas, in so far as they are suitable for quantitative spectrochemical analysis, together with the instrumentation required. Some important examples of the use of this technique in both science and industry are described.

Jakeman, E; Klewe, R C; Richards, P H; Walker, J G

doi: 10.1088/0022-3727/17/10/005pmid: N/A

The photon statistics of light scattered from an expanded laser beam which has passed through a laboratory propane flame are shown to be similar to those for light scattered from other deep random phase screens. The intensity fluctuations arise from the discrete eddy structure of the flame which Schlieren photographs confirm as having a broad size distribution. Intensity cross-correlation measurements using two point detectors positioned in the fluctuating scattered beam and at various distances from the flame give well defined velocities which in the near field are closely related to the convection velocity. It is also shown that when there are clearly defined regions of the flame with different mean convection velocities the cross-correlation measurements give separate results for each region.

Austin, M

doi: 10.1088/0022-3727/17/10/006pmid: N/A

The effect of changes in plate orientation on the resolution of holographic real images is studied experimentally. Resolution of 64 line pairs per mm was observed in the reconstructed real image from a hologram (NA 0.12, reconstruction beam angle 11 degrees ). Attainment of this performance required alignment of the plate to within 5 minutes of arc. Calculation of the aberration produced by a change in reference beam angle correlated with observed astigmatism and resolution.

Ong, E L; Roberts, A D

doi: 10.1088/0022-3727/17/10/007pmid: N/A

Sliding raw rubber against a rigid substrate can produce surface cracks in the rubber. The friction-induced rate of crack growth into the rubber bulk was found to be related to the tear energy of the particular grade of rubber under test, irrespective of its specimen geometry. The findings are relevant to the factory processing of raw rubber.

Penetrante, B M; Bardsley, J N

doi: 10.1088/0022-3727/17/10/008pmid: N/A

It is shown that, for the quasi-Lorentz gas model, there is no basis for doubting the correctness of the longitudinal diffusion coefficient DL, as obtained from the density gradient expanded solution of the Boltzmann equation. This conclusion is observed to hold true even for electrons in molecular gases where large inelastic processes are present. A corrected version of Lucas' (1970) derivation is shown to yield the same DL as that obtained from the density gradient expansion theories. Monte Carlo results for electrons in N2 and model CH4 are also presented and compared with existing simulation and Boltzmann solution results. The conclusions indicate that the calculations of DL in the Boltzmann code of Pitchford and Phelps (1982) are numerically in error.

Neger, T; Jager, H

doi: 10.1088/0022-3727/17/10/009pmid: N/A

Spatially resolving hook measurements are performed under appropriate conditions, yielding radial particle density distributions of different elements in a plasma column. This extension of the hook method was proved by using a Pfund type arc as a simple model for technical plasmas with rotational symmetry.

Kubono, T

doi: 10.1088/0022-3727/17/10/010pmid: N/A

The most probable mechanism for the cathode root on a mercury film which covers a solid metal anchor is suggested from comparison of the physical characteristics of mercury with those of the anchor metals. The numerical results calculated using the author's theory, i.e. the relationship between the arc current, the cathode-root radius, the cathode-root temperature, and the mercury evaporation rate, are shown schematically and compared with the experimental results of other investigators.