Degradation behaviour of a composite material for thermal protection systemsPart II Process simulation

Mass and energy balance equations have been solved in order to simulate the behavior of a silicon-based ablative composite used as a thermal protection shield for a non-animated space capsule. A method to calculate some of the parameters in the energy balance equation, is proposed, taking advantage of combined thermal analysis techniques. Furthermore, degradation kinetics in the hypothesis of constant volume is used to solve the mass balance. The results of the computer simulation are compared with the experimental data, obtained using plasma arc testing. The model can be used for both material selection and thickness calculation for thermal protection shields. © 1998 Kluwer Academic Publishers     

Acute phase toxoplasma abortions in sheep

Within 13 days of the experimental infection of 15 oestrus-synchronised ewes with 2000 sporulated oocysts of Toxoplasma gondii at 80 to 90 days of gestation 11 had aborted. The infection induced pyrexia and specific antibody in all the ewes. One ewe resorbed its fetus, 11 ewes aborted and three delivered, at full term, live congenitally infected lambs whose pre-colostral serum was antibody-positive. Tissues from the aborted fetuses and placentae from the live lambs were examined for toxoplasma infection by polymerase chain reaction (PCR) amplification of the B1 gene and by mouse inoculation. The live lambs were all shown to be infected by both methods, but there was no evidence of infection in any of the tissues from the acute phase abortions, suggesting that these fatalities occurred before the placenta or the fetus had been invaded by T gondii. Such toxoplasma-induced, acute-phase abortions are likely to be impossible to diagnose from fetal tissues. These results have implications not only for the diagnosis of naturally occurring ovine abortions but also for the understanding of the pathogenesis of toxoplasma-induced abortion.     

Measuring similarity in couples.

[Correction Notice: An erratum for this article was reported in Vol 16(3) of Journal of Family Psychology (see record 2007-17073-001). In the first paragraph on page 424, the formula to test whether the set of correlations significantly differs from one another is described incorrectly. The correct formula is to first transform the correlations with a Fisher's z transformation and to then compute the mean value of z. For each correlation, one then computes the deviation of z from the mean z, squares that deviation, and then sums the squares. This quantity is multiplied by k - 5, where k is the number of items used to compute the correlation. Under the null hypothesis that the correlations do not differ, the resulting quantity has a chi-square distribution with N - 3 degrees of freedom, where N is the number of couples. The test results reported in the article are unaffected as they appear to be based on the correct formula, rather than the incorrect one presented in the article.] The relationship between partner similarity and marital quality variables was explored by the use of a new method for the analysis of data from marital pairs. 42 married couples were given the Personal Assessment of Intimate Relationships inventory (M. T. Schaefer and D. H. Olson; see Pa, Vol 66:11686), and a method was devised for the removal of stereotype effects, that is, the tendency for partners to be similar to one another because they respond in a way that is typical of others. Similarity between wives and husbands decreased when adjusted for stereotype effects. There were no statistically significant relationships between couple similarity and measures of marital quality, with or without the adjustment for stereotype effects. However, there was evidence for both husbands and wives of an association between responding as typical husbands did and perceptions of satisfaction in the marital relationship. This result indicates that a stereotype effect may be a meaningful phenomenon rather than just a statistical artifact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human intelligence models and their implications for expert system structure and research

In order to determine the features which contribute to intelligent behaviour, several models of human intelligence were studied, This evaluation identified ten features present in human intelligent behaviour which may be relevant to expert systems design. These features were rated, by experts in the field of expert systems, on the extent of their presence in expert systems as compared with intelligent human behaviour. The four features receiving the lowest ratings were social competence, comprehension, automatization and memory management. The paper concludes with a discussion of these four features and outlines what needs to be done and why in order to incorporate them into the structure of expert systems.     

The effect of environmental pH on the failure strain of anodic films formed on the aluminum alloy 2024

The ultimate tensile strain of anodic films formed on 2024-T4 aluminum was evaluated as a function of pH in environments of 10⁻³M and 1·0M KNO₃, using resistive and capactive techniques. In the resistive technique, ultimate tensile strain was defined as the strain at which a discontinuous increase in anodic current was observed; in the capacitive technique, film failure was marked by a discontinuity in the slope of the capacitance versus strain curve. The ultimate tensile strain was seen to be significantly greater at the zero-point-of charge of the oxide (pH 8) than at higher or lower pH; in the capacitive measurements the ultimate tensile strain had an average value of 0·97 at pH 8 and 0·87 for measurements made at pH values of 4, 7 and 9. Dielectric behavior of the anodic films was seen to be different only in degree from that of films formed on pure aluminum. Changes in capacitance associated only with exposure were measured and taken into account. Capacitance behavior with strain was modeled by two linear regions; the first was attributed to elastic deformation of the film and the second, after failure, to the growth of regions of metal covered only with a thin, spontaneously-formed oxide.     

Metachromic interactions between azo and triphenylmethane dyes in aqueous solution. II. The effect of organic solvents on the interaction

The interaction between dilute aqueous solutions of the disazo dye Brilliant Orange and the triphenylmethane dye Crystal Violet results in a decrease in the absorption of Crystal Violet in the region 550–600 nm and the appearance of a new absorption at 494 nm. The decrease in absorbance at 590 nm is characteristic of the metachromic interactions of Crystal Violet with a wide variety of polyanion substrates while the increase at 494 nm is due to the conversion of Brilliant Orange from its azo to its hydrazone tautomer. The relative effects of a variety of organic solvents in reversing the interaction has been investigated.     

Overlay models in time-dependent non-linear material analysis

It is indicated how overlay models can be employed in time-dependent material studies. A basic component is employed which allows an instantaneous elastic response followed by viscous deformation, the onset of which is governed by the yield limit of a parallel friction slider. By combining several of these components in the form of overlays it is shown how several standard material behaviours can be reproduced. In particular the case of visco-elastic-plastic deformation is considered in detail. Numerical examples are provided.     

Thin plate semiloof element for structural analysis–including stability and natural vibrations

This paper presents a thin plate element formulated along parallel lines to the general three?dimensional Semiloof shell element. This plate version possesses only one half of the total number of degrees?of?freedom of the shell element and has the advantqage that the formulation of the strains and other terms is very much simplified. The element is first assessed in static situations and then its performance in the solution of eigenvalue problems is considered.