Target detection with a liquid crystal-based passive Stokes polarimeter

International audienceWe present an imaging system that measures the polarimetric state of the light coming from each point of a scene. This system, which determines the four components of the Stokes vector at each spatial location, is based on a liquid-crystal polarization modulator, which makes it possible to acquire fourdimensional Stokes parameter images at a standard video rate. We show that using such polarimetric images instead of simple intensity images can improve target detection and segmentation performance

The synergy of experiments and modeling to identify all monomer sequences and functional groups in copolymerization processes

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A detailed mechanistic study of bulk MADIX of styrene and its chain extension

The microstructural evolution of individual macrospecies during bulk macromolecular design by interchange of xanthates (MADIX) of styrene with (O-ethyl xanthate)-2-ethyl propionate as an initial agent (R0X) and its chain extension with fresh styrene or n-butyl acrylate (nBuA) is visualized in silico, allowing an unbiased (co)polymer product quality labelling according to monomer sequences and end-groups. Degenerative transfer coefficients for both exchange with R0X (Ctr,0) and macro-RAFT agent (Ctr) are reported (Ctr,0 = 0.80 ± 0.02; Ctr: 0.44 ± 0.07) by applying multi-response regression analysis to the experimental data on the RAFT agent and styrene conversion, number and mass average molar masses, and end-group functionality (EGF). The EGF data are obtained by combining dialysis to remove residual R0X species and elemental analysis. It is shown that the MADIX mechanism can be properly understood only by explicitly acknowledging the differences in exchange reactivities and that the macroradical homopolymer CLD follows a Flory–Schulz distribution, which is an exception for controlled reversible addition–fragmentation chain transfer polymerization. Moreover, for the selected monomer conversion ranges, both “blocks” of the chain extension are formed through a single exchange

Optimizing P300-speller sequences by RIP-ping groups apart

International audienceSo far P300-speller design has put very little emphasis on the design of optimized flash patterns, a surprising fact given the importance of the sequence of flashes on the selection outcome. Previous work in this domain has consisted in studying consecutive flashes, to prevent the same letter or its neighbors from flashing consecutively. To this effect, the flashing letters form more random groups than the original row-column sequences for the P300 paradigm, but the groups remain fixed across repetitions. This has several important consequences, among which a lack of discrepancy between the scores of the different letters. The new approach proposed in this paper accumulates evidence for individual elements, and optimizes the sequences by relaxing the constraint that letters should belong to fixed groups across repetitions. The method is inspired by the theory of Restricted Isometry Property matrices in Compressed Sensing, and it can be applied to any display grid size, and for any target flash frequency. This leads to P300 sequences which are shown here to perform significantly better than the state of the art, in simulations and online tests