Showing papers by "Université Nantes Angers Le Mans published in 2010"

Shedding new light on Hierarchical Principal Component Analysis

Abstract: Hierarchical Principal Component Analysis (HPCA) is a multiblock method which is designed to reveal covariant patterns between and within several multivariate datasets. The computation of the parameters of this method, namely block scores, block loadings, global loadings and global scores, is based on an iterative procedure. However, very few properties are known regarding the convergence of this iterative procedure. The paper discloses a monotony property of HPCA and exhibits an optimization criterion for which HPCA algorithm provides a monotonic convergent solution. This makes it possible to shed a new light on this method of analysis by showing new properties and pinpointing its relation to existing methods such as Common Component and Specific Weights Analysis (CCSWA), INDSCAL and PARAFAC Models. Copyright © 2010 John Wiley & Sons, Ltd.

Mechanisms of Particle Deposition in Ventilation Ducts for a Food Factory

Abstract: An improved Eulerian model is proposed to predict particle deposition velocity in a typical mechanical ventilation system of a dairy food factory. For fully developed turbulent flow, the model is modified based on the three-layer model developed by Zhao and Wu (2006a), accounting for thermophoresis as well as turbophoresis, Brownian diffusion, turbulent diffusion, and gravitational settling. Based on in-situ measurements of the aerosol size distributions, particles discussed in this article were in the size range 0.3–20 μm. The measured mass concentration and the predicted particle deposition velocity were used to calculate the deposited particle mass flux in the ventilation duct. The results indicate that the effects of temperature gradients and of surface roughness should be considered in food factories ventilation ducts. For horizontal surfaces, it is shown that even a little difference between empirical and theoretical models can lead to a 2-fold difference in the predicted deposited particle mass flu...

Unpolarized emissivity of thin oil films over anisotropic Gaussian seas in infrared window regions

Abstract: In this paper, we derive the unpolarized infrared (IR) emissivity of thin oil films over anisotropic Gaussian seas from a refined physical surface spectrum model of damping due to oil. Since the electromagnetic wavelength is much smaller than the surface mean curvature radius and than the surface root mean square height, the Kirchhoff-tangent plane approximation, reduced to the geometric optics approximation, can be used. The surface can then be replaced by its local infinite tangent plane at each point of each rough surface. The multiple reflections at each interface are ignored (i.e., for both the upper air/oil interface and the lower oil/sea interface of the contaminated sea). Nevertheless, the multiple reflections between the upper and the lower interfaces of the oil film are taken into account, by assuming a locally flat and planar thin oil film, which forms a local Fabry-Perot interferometer. This means that the Fresnel reflection coefficient of a single interface can be substituted for the equivalent Fresnel reflection coefficient of the air/oil/sea film, calculated by considering an infinite number of reflections inside the layer. Comparisons of the emissivity between a clean sea and a contaminated sea are presented, with respect to emission angle, wind speed, wind direction, oil film thickness, oil type, and wavelength. Thus, oil detection, characterization, and quantization are investigated in the IR window regions.

Extension of the roughness criterion of a one-step surface to a one-step layer

Abstract: The problem of electromagnetic wave scattering from a one-step surface is a well-known subject. The reflected power can be evaluated using the widely-used Rayleigh roughness parameter. Here, its extension to the case where the one-step surface overlies a perfectly flat surface, called one-step layer, is studied.