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Estimating the replacement potential of Norwegian high-speed passenger vessels with zero-emission solutions
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Stoichiometry-Controlled Reversible Lithiation Capacity in Nanostructured Silicon Nitrides Enabled by in Situ Conversion Reaction
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Synthesis, Structure and NH3 Sorption Properties of Mixed Mg1-xMnx(NH3)6Cl2 Ammines
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Interactions between Asphaltenes and a Model Demulsifier in Bulk and at an Interface Studied by Small-Angle Neutron Scattering (SANS) and Neutron Reflectometry
Get PDFThis article describes neutron reflectometry to probe the structure of the asphaltene layer adsorbed onto a hydrophilic silicon surface and the interactions between asphaltenes and a model demulsifier (pluronic). To start with, asphaltene nanoaggregation is studied in bulk by small-angle neutron scattering (SANS). In pure toluene, asphaltenes form nanoaggregates with sizes that are found to moderately increase when heptane is added. Then, the structure of the asphaltene layer onto a silicon surface is determined by neutron reflectometry. It is first shown that conclusive results on the structure of the adsorbed asphaltene layer can only be determined by varying the scattering length density of the solvent, i.e., by measuring reflectivity curves in various mixtures of D- and H-toluene and by simultaneously fitting all the data sets. The asphaltene layer can be successfully modeled using a single layer; a two-layer model always converges with the second layer having zero thickness. This layer has a thickness of 51 Å, with a low solvation close to the silicon surface (estimated ≈29%). The solvation increases with distance from the silicon oxide layer, reaching finally a value of 91%. Small-angle neutron scattering data indicate that the thickness is close to twice the radius of gyration of asphaltene nanoaggregates in solution. This result indicates that the extent of the asphaltene layer is linked to its self-associative properties in bulk. Finally, using the results obtained by contrast matching to constrain the fitting, the influence of a model demulsifier (pluronic PE 8100) on the asphaltene layer is investigated. In the presence of pluronic, the layer does not protrude as far into the bulk (thickness is reduced) and becomes rougher due to the partial incorporation of pluronic.submittedVersionacceptedVersio
Accounting for effects of variation in luminance in pupillometry for field measurements of cognitive workload
Get PDFEye-tracking is now above and beyond the sole measurement of visual attention. Amongst the multiple measures it provides, some have been explored as a measure of cognitive workload (CW). One such measure is pupil diameter. Although the relationship between pupil size and CW has been extensively documented, pupil diameter is primarily impacted by luminance variations while the cognitive workload has a relatively minor influence. Therefore luminance variations have to be accounted for, either in the experimental design or in the data processing to avoid the masking of the CW effects. This has meant that the use of pupillometry for the measurement of anything but the pupillary light response, has been restricted to highly controlled lighting conditions in a laboratory. This study proposes a new method that uses point of view (POV) video in conjunction with a luminance measurement sensor to dynamically estimate the luminance of the visual stimuli. As currently available off the shelf eye trackers are usually not equipped to record luminance variations, a luminance sensor was added to a commercial eye tracker. Eye-tracking gaze data, POV video recording of the operator/observer and a head-mounted (POV) luminance sensor together estimate the expected pupil diameter. This estimate over time is due to sole influence of luminance variations. This expected pupil diameter is used as baseline for the cognitive workload. The method was validated in laboratory conditions with controlled visual stimuli. The method reliably measures induced cognitive workload despite luminance variation.acceptedVersio
