173 research outputs found

    From tacit knowledge to visual expertise: Eye-tracking support in maritime education and training

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    The maritime pilot is an expert with knowledge on a specific navi- gational route. The maritime pilot cadet undergoes maritime education and training in classrooms, onboard vessels and in simulators. Developing visual expertise is a basic objective. Transferring knowledge from experienced mar- itime pilots to maritime pilot cadets is challenging since some of this knowledge is tacit. The transference is achieved by externalization and socialization pro- cesses. The objective of this pre-study was to assess eye-tracking methodology as a tool to support maritime education and training, and for transferring tacit knowledge. The study was performed in an explorative way during simulator sessions, by interviews, questionnaires and observations. The result shows that eye-tracking methodology is useful for transferring tacit knowledge in simulator settings, but not during other parts of the education and training. The results also show that situational awareness of maritime pilot instructors and maritime pilot cadets increases when utilizing eye-tracking methodology

    Selective ultrafast probing of transient hot chemisorbed and precursor states of CO on Ru(0001)

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    We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell’Angela et al. Science 339 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2  ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process

    X-ray Diffraction and Molecular Dynamics Study of Medium-range Order in Ambient and Hot Water

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    We have developed x-ray diffraction measurements with high energy-resolution and accuracy to study water structure at three different temperatures (7, 25 and 66 C) under normal pressure. Using a spherically curved Ge crystal an energy resolution better than 15 eV has been achieved which eliminates influence from Compton scattering. The high quality of the data allows a precise oxygen-oxygen pair correlation function (PCF) to be directly derived from the Fourier transform of the experimental data resolving shell structure out to ~12 {\AA}, i.e. 5 hydration shells. Large-scale molecular dynamics (MD) simulations using the TIP4P/2005 force-field reproduce excellently the experimental shell-structure in the range 4-12 {\AA} although less agreement is seen for the first peak in the PCF. The Local Structure Index [J. Chem. Phys. 104, 7671 (1996)] identifies a tetrahedral minority giving the intermediate-range oscillations in the PCF and a disordered majority providing a more featureless background in this range. The current study supports the proposal that the structure of liquid water, even at high temperatures, can be described in terms of a two-state fluctuation model involving local structures related to the high-density and low-density forms of liquid water postulated in the liquid-liquid phase transition hypothesis.Comment: Submitted to Phys. Chem. Chem. Phy

    Strong Influence of Coadsorbate Interaction on CO Desorption Dynamics on Ru(0001) Probed by Ultrafast X-Ray Spectroscopy and \u3cem\u3eAb Initio\u3c/em\u3e Simulations

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    We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5σ and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process
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