On the threshold pinning force in type II superconducting films

The maximum pinning force of a two-dimensional vortex lattice in a random potential is calculated. A connection is established between this threshold pinning force and the potential energy discontinuities due to elastic and plastic instabilities of the vortex lattice. Inspired by recent computer simulations, we assume that the fluctuations in the commensurability between the random potential and the vortex potential breaks the vortex system up into a set of flowing channels in between trapped regions. Two instability mechanisms and their contribution to the threshold force are discussed within this channel-flow picture. We find that three different regimes exist depending on, w, the width of the channels;w=,a ₀w=a ₀ , wherea ₀ is the vortex lattice spacing. Weak pinning superconductors can pass through all three regimes as the reduced magnetic field is varied from 0 to 1, whereas strong pinning compounds can remain in the saturated region (w=a ₀ ) for all values of the field. We compare the expression for the threshold force with experimental results for both strong and weak pinning samples. A satisfactory qualitative agreement is obtained between theory and experiment.     

Self-Consistent Model for Planar Ferrite Growth in Fe-C-X Alloys

A self-consistent model for non-partitioning planar ferrite growth from alloyed austenite is presented. The model captures the evolution with time of interfacial contact conditions for substitutional and interstitial solutes. Substitutional element solute drag is evaluated in terms of the dissipation of free energy within the interface, and an estimate is provided for the rate of buildup of the alloying element “spike” in austenite. The transport of the alloying elements within the interface region is modeled using a discrete-jump model, while the bulk diffusion of C is treated using a standard continuum treatment. The model is validated against ferrite precipitation and decarburization kinetics in the Fe-Ni-C, Fe-Mn-C, and Fe-Mo-C systems.     

Development of an experimental technique to assess the permeability of metal coated polymer films

The experimental time required to measure water vapour permeability of barrier film using the cup method is extremely long. In this study, a new technique is proposed, based on light transmission. This fast and accurate method was first validated using model films constituted of aluminized PET (polyethylene terephthalate) with aluminium layers of different thicknesses (<100 nm). It was possible to show that the ‘illuminating’ method could advantageously be employed to control the film’s barrier properties during their fabrication. In a second step, the method was tentatively used to measure the changes in barrier properties over time, when the samples are submitted to severe hydrothermal ageing (70 °C, 90% relative humidity [RH]). It was concluded that the complex degradation mechanism prevents accurate measurement while ageing.     

Determination of Materials Selection Performance Indices Through the Combination of Numerical Modeling and Optimization Methods

After translation, the first stages traditionally involved in the materials selection are filtration and classification, which require formulation of criteria (constraints or objectives) deduced from information written in the set of material requirements. These criteria, which are representative of the behavior of the material and the studied structure, must be formulated analytically in order to be used during selection stage. However, for complex behavior, analytical processing of models is no longer possible and it can be replaced by a combination of numerical resolution methods and an optimization method which make it possible to obtain approximate formal expressions of the criteria. In this paper, a complete selection method is proposed. The method is applied to the constraints as well as the objectives, in order to carry out the filtration and classification stages at the same time. The study of the thermomechanical behavior of a machine tool frame has been used to demonstrate the validity of the proposed method.     

Expression des émotions dans le dessin d'un homme chez l'enfant de 5 à 11 ans.

This study examines the development of children's ability to express emotions in their human figure drawing. Sixty children of 5, 8, and 11 years were asked to draw "a man," and then a "sad", "happy," "angry" and "surprised" man. Expressivity of the drawings was assessed by means of two procedures: a limited choice and a free labelling procedure. Emotionally expressive drawings were then evaluated in terms of the number and the type of graphic cues that were used to express emotion. It was found that children are able to depict happiness and sadness at 8, anger and surprise at 11. With age, children use increasingly numerous and complex graphic cues for each emotion (i.e., facial expression, body position, and contextual cues). Graphic cues for facial expression (e.g., concave mouth, curved eyebrows, wide opened eyes) share strong similarities with specific "action units" described by Ekman and Friesen (1978) in their Facial Action Coding System. Children's ability to depict emotion in their human figure drawing is discussed in relation to perceptual, conceptual, and graphic abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On velocity and spacing selection in discontinuous precipitation-I. Simplified analytical approach

A new approach is proposed to the problem of pattern selection in discontinuous precipitation. It relies on the simultaneous calculation of growth velocities for both the precipitate lamellae and the interlamellar solid solution phase, and on the recognition that the processes of diffusional transport along grain boundaries and interphase boundaries are fundamentally different. The first is considered governed by lateral gradients of concentration, the second by gradients of curvature. It is shown that the simple hypotheses of thermodynamic equilibrium and diffusive flux continuity at the triple junction between the precipitate lamella and the initial and depleted parent phases (along with the requirement that the two phases grow at the same rate) is sufficient to remove the degeneracy of the problem; the new treatment provides a selection of spacing and transformation front velocity consistent with experimental results in the literature.     

Characterization and Modeling of Precipitation Kinetics in a Fe-Si-Ti Alloy

In this article, we present a systematic study of precipitation kinetics in a Fe-Si-Ti alloy in the temperature range 723?K to 853?K (450?°C to 580?°C), combining complementary tools (transmission electron microscopy (TEM), atom probe tomography (APT), and small-angle neutron scattering (SANS)). We show that the Heusler phase Fe₂SiTi dominates the precipitation process in the investigated time and temperature range, regardless of the details of the initial temperature history. A numerical model based on the evolution of precipitate size classes gives very good agreement with the experimental results, and its application to different alloy compositions provides directions for future alloy optimization.     

Study of the compatibility between criteria in a set of materials requirements: Application to a machine tool frame

This contribution to materials selection theory aims at developing methodological methods and tools to analyse a complex set of material requirements with the objective of forecast whether there are materials that can fulfil it, or alternatively, if multi-materials selection is more likely to provide a solution. This “pre-analysis” of requirements examines the two main reasons which may prevent a single material solution: nonuniformity of materials space filling, or intrinsic contradiction between properties.A variety of statistical tools is used, based on Multivariate Analysis Methods as Principal Component Analysis (PCA) and the estimation of density distribution in the materials space. These tools allow to evaluate the “statistical compatibility” between the requirements and the available materials, and provides an estimate of the likelihood to find a single material solution or not. The methodology is applied to the research of a material for a machine tool frame.