Olivier Lavialle

Fatty acid composition of pinaceae as taxonomic markers

Following our previous review on Pinus spp. seed fatty acid (FA) compositions, we recapitulate here the seed FA compositions of Larix (larch), Picea (spruce), and Pseudotsuga (Douglas fir) spp. Numerous seed FA compositions not described earlier are included. Approximately 40% of all Picea taxa and one-third of Larix taxa have been analyzed so far for their seed FA compositions. Qualitatively, the seed FA compositions in the three genera studied here are the same as in Pinus spp., including in particular the same Δ5-olefinic acids. However, they display a considerably lower variability in Larix and Picea spp. than in Pinus spp. An assessment of geographical variations in the seed FA composition of P. abies was made, and intraspecific dissimilarities in this species were found to be of considerably smaller amplitude than interspecific dissimilarities among other Picea species. This observation supports the use of seed FA compositions as chemotaxonomic markers, as they practically do not depend on edaphic or climatic conditions. This also shows that Picea spp. are coherently united as a group by their seed FA compositions. This also holds for Larix spp. Despite a close resemblance between Picea and Larix spp. seed FA compositions, principal component analysis indicates that the minor differences in seed FA compositions between the two genera are sufficient to allow a clear-cut individualization of the two genera. In both cases, the main FA is linoleic acid (slightly less than one-half of total FA), followed by pinolenic (5,9,12-18:3) and oleic acids. A maximum of 34% of total Δ5-olefinic acids is reached in L. sibirica seeds, which appears to be the highest value found in Pinaceae seed FA. This apparent limit is discussed in terms of regio- and stereospecific distribution of Δ5-olefinic acids in seed triacylglycerols. Regarding the single species of Pseudotsuga analyzed so far (P. menziesii), its seed FA composition is quite distinct from that of the other two genera, and in particular, it contains 1.2% of 14-methylhexadecanoic (anteiso-17:0) acid. In the three genera studied here, as well as in most Pinus spp., the C18Δ5-olefinic acids (5,9-18:2 and 5,9,12-18:3 acids) are present in considerably higher amounts than the C20Δ5-olefinic acids (5,11-20:2 and 5,11,14-20:3 acids).

Consideration of obstacle danger level in path planning using A* and fast-marching optimisation: comparative study

Obstacle danger level is taken into consideration in path planning using fractional potential maps. This paper describes the two optimisation methods tested: the A* algorithm and the Fast-Marching technique. The efficiency of the two approaches is illustrated and compared through a vehicle path planning application in a fixed obstacle environment. A* is a heuristically ordered research algorithm and is complete and admissible. Fast-Marching provides a convex map without local minima and permits real-time evaluation of optimal trajectories. A vehicle path planning application is considered in a fixed obstacle environment. A specific danger level is given to each obstacle. The obtained continuous curve trajectories are compared.

Multifocus image fusion and denoising: A variational approach

In this letter we propose a variational approach for concurrent image fusion and denoising of multifocus images, based on error estimation theory and Partial Differential Equations (PDEs). In real world scenarios the assumption that the inputs of an image fusion process contain only useful information, pertinent to the desired fused output, does not hold true more often than not. Thus, the image fusion problem needs to be addressed from a more complex, fusion-denoising point of view, in order to provide a fused result of greater quality. The novelty of our approach consists in defining an image geometry-driven, anisotropic fusion model, numerically expressed using an anisotropy-reinforcing discretization scheme that further increases the anisotropic behavior of the proposed fusion paradigm. The preliminary experimental analysis shows that robust anisotropic denoising can be attained in parallel with efficient image fusion, thus bringing two paramount image processing tasks into complete synergy. One immediate application of the proposed method is fusion of multifocus, noise-corrupted images.

Flow coherence diffusion. linear and nonlinear case

The paper proposes a novel tensor based diffusion filter, dedicated for filtering images composed of line like structures. We propose a linear version of nonlinear diffusion partial derivative equation, previously presented in [5]. Instead of considering nonlinearity in the image evolution process we are only including it at the computation of the diffusion tensor. The unique tensor construction is based on an adaptive orientation estimation step and yields a significant reduction of the computational complexity. The properties of the filter are analyzed both theoretically and experimentally.

Discontinuous seismic horizon tracking based on a poisson equation with incremental dirichlet boundary conditions

We propose a new method to track a seismic horizon with a discontinuity due to a fault throw assumed to be quasi-vertical. Our approach requires the knowledge of the two points delimiting the horizon as well as the discontinuity location and jump. We deal with a non linear partial derivative equation relied on the estimated local dip. Its iterative resolution is based on a Poisson equation with incremental Dirichlet boundary conditions. By exploiting a coherence criterion, we finally present an efficient method even when the discontinuity location and jump are unknown.

Coherence enhancing image sharpening and denoising using a novel shock filter model

We present a new approach based on Partial Differential Equations (PDEs) and shock filter theory for image enhancement in “Gaussian Blur (GB) + Additive White Gaussian Noise (AWGN)” scenarios. The main disadvantage of shock filters, inability of successfully filtering noisy images, is overcome by the introduction of a complex shock filter framework. The proposed method allows for better control and anisotropic shock filtering, via its control functions f1 and f2. The main advantages of our method consist in the ability of successfully enhancing GB+AWGN images while exhibiting a coherence enhancing behavior.

Seismic fault detection using marked point processes

A stochastic model for fault detection in 2D sections of seismic blocks is presented. The model is a marked point process in which each fault is modeled by a parabola.