Multiple-relaxation-time lattice Boltzmann models in three dimensions

This article provides a concise exposition of the multiple-relaxation-time lattice Boltzmann equation, with examples of 15-velocity and 19-velocity models in three dimensions. Simulation of a diagonally lid-driven cavity flow in three dimensions at Re = 500 and 2000 is performed. The results clearly demonstrate the superior numerical stability of the multiple-relaxation-time lattice Boltzmann equation over the popular lattice Bhatnagar-Gross-Krook equation.     

Apodized fiber Bragg gratings manufactured with the phase plate process

We present a manufacturing method based on the dynamic use of phase plates to photowrite Bragg gratings. This process allows for control of the local value of the index modulation envelope in the grating. The application to apodized fiber Bragg gratings is discussed.     

Effectiveness of simultaneous independent realizations at low carrier-to-noise ratio to improve heterodyne Doppler lidar performance. I. Theory and numerical simulations

It is shown that the performance of heterodyne Doppler lidar (HDL) can be improved by (i) at least one good realization for every single shot or (ii) several simultaneous good realizations for accumulation. Until now, several simultaneous independent realizations at high carrier-to-noise ratio (CNR) have been considered. At low CNR, noise may have a detrimental effect on the accumulation techniques. We determine the chances of getting "heavy" speckles in HDL signals from many receiver-detector units on a single-shot basis and several good realizations on a single-shot basis, which is required for an effective accumulation. The use of multiple receiver-detector units at low CNR is worthwhile in contexts such as space lidar, where optimized treatment is at a premium. We conclude on the effectiveness of many receiver-detector units in parallel in order to achieve simultaneous independent realizations at low CNR to improve the performance of HDL on a statistical basis.     

Photobleaching of a solid photochromic medium by a Gaussian laser beam

Equations that describe the photobleaching of photochromic layers illuminated by Gaussian laser beams are given. The photochromic samples are made of thionine, triethanolamine, and polyvinyl alcohol and follow simple kinetics law. Spatial absorbance and time-dependent power transmittance are well described by the developed equations. The model is used to calculate the Gaussian dimension of helium-neon laser beams from kinetics data.     

Population computation of vectorial transformations

Many neurons of the central nervous system are broadly tuned to some sensory or motor variables. This property allows one to assign to each neuron a preferred attribute (PA). The width of tuning curves and the distribution of PAs in a population of neurons tuned to a given variable define the collective behavior of the population. In this article, we study the relationship of the nature of the tuning curves, the distribution of PAs, and computational properties of linear neuronal populations. We show that noise-resistant distributed linear algebraic processing and learning can be implemented by a population of cosine tuned neurons assuming a nonuniform but regular distribution of PAs. We extend these results analytically to the noncosine tuning and uniform distribution case and show with a numerical simulation that the results remain valid for a nonuniform regular distribution of PAs for broad noncosine tuning curves. These observations provide a theoretical basis for modeling general nonlinear sensorimotor transformations as sets of local linearized representations.     

Strain-dependent recovery of spontaneous hindlimb movement in spinal cord transected mice (CD1, C57BL/6, BALB/c).

Reorganization and plasticity after spinal cord injury have been recently shown to take place in sublesional neuronal networks, but the possibility of strain-dependent changes at that level has never been explored. The authors studied the spontaneous return of hindlimb movement in low-thoracic spinal cord transected (Tx) mice from 3 commonly used strains. Without intervention, most CD1, C57BL/6, and BALB/c mice displayed some hindlimb movement recovery after Tx. Although all assessment methods unanimously reported that CD1 displayed higher recovery levels than did the C57BL/6 and BALB/c, higher scores were generally found with the Antri-Orsal-Barthe (M. Antri, D. Orsal, & J. Y. Barthe, 2002) and the Average Combined Score (P. A. Guertin, 2005a) methods. Such spontaneous recovery in low-thoracic Tx mice is likely the result of neuronal plasticity at the lumbosacral spinal cord level, suggesting that these sublesional changes are strain dependent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correction to Perruchet et al. (2006).

Reports an error in "Do We Need Algebraic-Like Computations? A Reply to Bonatti, Pena, Nespor, and Mehler (2004)" by Pierre Perruchet, Ronald Peereman, and Michael D. Tyler (Journal of Experimental Psychology: General, 2006[May], 135(2), 322-326). The page numbers that Dr. Perruchet cited from Dr. Bonatti et al.'s article were printed incorrectly. These page numbers should appear as follows in the correction. (The following abstract of this article originally appeared in record 2006-06642-011.) L. L. Bonatti, M. Pena, M. Nespor, and J. Mehler (see record 2006-06642-010) argued that P. Perruchet, M. D. Tyler, N. Galland, and R. Peereman (see record 2004-21166-008) confused the notions of segmentation and generalization by ignoring the evidence for generalization in M. Pena, L. L. Bonatti, M. Nespor, and J. Mehler (see record 2002-06215-001). In this reply, the authors reformulate and complement their initial arguments, showing that their way of dealing with segmentation and generalization is not due to confusion or ignorance but rather to the fact that the tests used in Pena et al. make it likely that neither segmentation nor generalization were captured in their experiments. Finally, the authors address the challenge posed by Pena et al. of accounting for the whole pattern of their results without invoking rule-based, algebraic-like computations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymptotic global confidence regions for 3-D parametric shape estimation in inverse problems.

This paper derives fundamental performance bounds for statistical estimation of parametric surfaces embedded in R3. Unlike conventional pixel-based image reconstruction approaches, our problem is reconstruction of the shape of binary or homogeneous objects. The fundamental uncertainty of such estimation problems can be represented by global confidenceregions, which facilitate geometric inference and optimization ofthe imaging system. Compared to our previous work on global confidence region analysis for curves [two-dimensional (2-D) shapes], computation of the probability that the entire surface estimate lies within the confidence region is more challenging because a surface estimate is an inhomogeneous random field continuously indexed by a 2-D variable. We derive an asymptotic lower bound to this probability by relating it to the exceedence probability of a higher dimensional Gaussian random field, which can, in turn, be evaluated using the tube formula due to Sun. Simulation results demonstrate the tightness of the resulting bound and the usefulness of the three-dimensional global confidence region approach.     

Elastoplastic Model for the Long-Term Behavior Modeling of Unbound Granular Materials in Flexible Pavements

The constitutive modeling of cyclic plasticity of soils has made great progress, especially in the area of sands liquefaction modeling. Nowadays, the problem of rutting of flexible pavements linked to permanent deformations occurring in the unbound layers is taken into account only by empirical formulas. This paper presents an elastoplastic model with both isotropic and kinematic hardening. The yield surface, plastic potential, and isotropic hardening are based on a model for sands, which takes into account the influence of the initial void ratio and of the mean stress on the mechanical behavior. A kinematic hardening has been added in order to take into account the mechanical behavior of the material for large cycle numbers. A complete model is then developed, simulations are presented, and comparisons with repeated load triaxial tests carried out on a subgrade soil (clayey sand), have been made. These comparisons underline the capabilities of the model to take into account the monotonic, cyclic, and ratchetting behavior of unbound materials for roads.