Corrosion behaviour of low-Si alloyed steels in neutral reducing conditions at 90 °C

Electrochemical investigations on low-Si alloyed steels with Si content ranging from 0.25 to 3.2 wt.% were carried out in a 0.1 M NaCl borate-buffered solution (pH 8.4) in reducing conditions at 90 °C. Silicon as an alloying element was proved to degrade at first the steel ability to passivate. For longer immersion times, protective effects developed more efficiently on the steel containing 3.2 wt.% silicon. Passive layers electrochemically formed in the transpassive domain on the steel containing 3.2% Si were shown to be significantly different from those grown at rest potential.     

Prediction of swirling confined diffusion flame with a Monte Carlo and a presumed-PDF-model

This work aims to compare numerical results obtained by using the Monte Carlo composition-PDF method and a presumed-β-PDF in order to reveal their effects on the prediction of flow and scalar fields in swirling confined methane diffusion flame. Using the intrinsic low dimensional manifolds method for modelling the chemistry and a second moment closure for the turbulence, it is shown that both PDF-methods provide a similar accuracy level of the prediction of mean quantities. While the presumed-β-PDF performs using reasonable computational efforts, the Monte Carlo-PDF allows to capture well the turbulence-chemistry interaction and strong finite-chemistry effects such as local extinction.     

Symmetry-breaking transitions in equilibrium shapes of coherent precipitates: Effect of elastic anisotropy and inhomogeneity

We examine the symmetry-breaking transitions in equilibrium shapes of coherent precipitates in two-dimensional (2-D) systems under a plane-strain condition with the principal misfit strain components ε* _xx and ε* _yy . For systems with cubic elastic moduli, we first show all the shape transitions associated with different values of t=ε* _yy /ε* _xx . We also characterize each of these transitions, by studying its dependence on elastic anisotropy and inhomogeneity. For systems with dilatational misfit (t=1) and those with pure shear misfit (t=−1), the transition is from an equiaxed shape to an elongated shape, resulting in a break in rotational symmetry. For systems with nondilatational misfit (−1<t<1; t ≠ 0), the transition involves a break in mirror symmetries normal to the x- and y-axes. The transition is continuous in all cases, except when 0<t<1. For systems which allow an invariant line (−1≤t<0), the critical size increases with an increase in the particle stiffness. However, for systems which do not allow an invariant line (0<t≤1), the critical size first decreases, reaches a minimum, and then starts increasing with increasing particle stiffness; moreover, the transition is also forbidden when the particle stiffness is greater than a critical value.     

Bounds on the number of samples needed for neural learning.

The relationship between the number of hidden nodes in a neural network, the complexity of a multiclass discrimination problem, and the number of samples needed for effect learning are discussed. Bounds for the number of samples needed for effect learning are given. It is shown that Omega(min (d,n) M) boundary samples are required for successful classification of M clusters of samples using a two-hidden-layer neural network with d-dimensional inputs and n nodes in the first hidden layer.     

K-winner networks.

A special class of mutually inhibitory networks is analyzed, and parameters for reliable K-winner performance are presented. The network dynamics are modeled using interactive activation, and results are compared with the sigmoid model. For equal external inputs, network parameters that select the units with the larger initial activations (the network converges to the nearest stable state) are derived. Conversely, for equal initial activations, networks that select the units with larger external inputs (the network converges to the lowest energy stable state) are derived. When initial activations are mixed with external inputs, anomalous behavior results. These discrepancies are analyzed with several examples. Restrictions on initial states are derived which ensure accurate K-winner performance when unequal external inputs are used.     

Intelligent identification and control for autonomous guided vehicles using adaptive fuzzy-based algorithms

Fuzzy logic was first suggested as the mechanism by which humans drive cars. This paper addresses the use of fuzzy logic and algorithms towards the intelligent autonomous motion control of land vehicles. To cope with vehicle complexities, internal parametric changes, and with unpredictable environmental effects, the controllers that are presented, whilst heuristic in nature, are self-organizing or self-learning in that they generate automatically by observation an experiential rule base that models the vehicle, and via an appropriate performance index an optimal control rule base that is robust to large parametric changes. The methodology presented is applicable to any complex process which is too difficult to model or control using conventional methods, or which has relied on the experience of a human operator. An overview of fuzzy logic and static fuzzy logic control (akin to expert systems) is provided, together with illustrative examples.     

Three ways to implement interfacial techniques: application tomeasurements of chromatic dispersion, birefringence, and nonlinearsusceptibilities

Depending on the spectal width of the source illuminating an interferometer, measurement procedures can utilize either the whole interferogram, or only the fringe envelope, or only the fringe quick oscillations. With an ultraband spectrum source, a simplified adaptation of the methods of Fourier transform spectroscopy yields the variations of the test-fiber propagation constant over the whole wavelength-interval of the source. Chromatic dispersion can then be computed from a single interferogram. With narrower spectrum sources, only the fringe envelopes are utilized and yield measurements of mode delay, with application to chromatic and polarization mode dispersion. In this case, however, interferograms at several wavelengths are necessary. With even narrower spectrum sources, the fringe quick oscillations provide measurements of phase shifts, related to changes in the mode propagation constant, when outside perturbations are applied to the test fiber. A direct method for measuring the third-order nonlinear susceptibilities is discussed. In this case the outside perturbation is an intense pump laser field