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Browsing by Issue Date, starting with "2004-09-01"

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  • Capillary bridging and long-range attractive forces in a mean-field approach
    Publication . Andrienko, D.; Patricio, Pedro; Vinogradova, O. I.
    When a mixture is confined, one of the phases can condense out. This condensate, which is otherwise metastable in the bulk, is stabilized by the presence of surfaces. In a sphere-plane geometry, routinely used in atomic force microscope and surface force apparatus, it, can form a bridge connecting the surfaces. The pressure drop in the bridge gives rise to additional long-range attractive forces between them. By minimizing the free energy of a binary mixture we obtain the force-distance curves as well as the structural phase diagram of the configuration with the bridge. Numerical results predict a discontinuous transition between the states with and without the bridge and linear force-distance curves with hysteresis. We also show that similar phenomenon can be observed in a number of different systems, e.g., liquid crystals and polymer mixtures. (C). 2004 American Institute of Physics.
    2004-09-01Journal article Restricted access Show more
  • Optical confinement and colour separation in a double colour laser scanned photodiode (D/CLSP)
    Publication . Vieira, Manuela; Fernandes, Miguel; Louro, Paula; Fantoni, Alessandro; Rodrigues, Isabel Maria Cabrita
    Large area n-i-p-n-i-p a-SiC:H heterostructures are used as sensing element in a double colour laser scanned photodiode image sensor (D/CLSP). This work aims to clarify possible improvements, physical limits and performance of CLSP image sensor when used as non-pixel image reader. Here, the image capture device and the scanning reader are optimized and the effects of the sensor structure on the output characteristics discussed. The role of the design of the sensing element, the doped layer composition and thickness, the read-out parameters (applied voltage and scanner frequency) on the image acquisition and the colour detection process are analysed. A physical model is presented and supported by a numerical simulation of the output characteristics of the sensor.
    2004-09-01Journal article Open access Show more