Displaying all 4 publications

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  1. Chen LC, Low AL, Chien SF
    Appl Opt, 2004 Dec 10;43(35):6380-3.
    PMID: 15617273
    We propose the use of a truncated ball lens in a collimating system to transform a spherical wave from a highly divergent source into a plane wave. The proposed scheme, which incorporates a hyperbolic lens, is discussed, and the overall system is found to have a large acceptance angle and to be free of spherical aberration. Diffraction and polarization effects are neglected, as well as skew rays.
  2. Chen LC, Low AL, Chien SF
    Appl Opt, 2004 Nov 10;43(32):5923-5.
    PMID: 15587718
    A novel fiber tapering shape, which is based on compound parabolic geometry, is proposed to increase the acceptance angle of a compound parabolic concentrator. The proposed design is described by use of ray optics on a step-index multimode fiber.
  3. Yau KL, Poh GS, Chien SF, Al-Rawi HA
    ScientificWorldJournal, 2014;2014:209810.
    PMID: 24995352 DOI: 10.1155/2014/209810
    Cognitive radio (CR) enables unlicensed users to exploit the underutilized spectrum in licensed spectrum whilst minimizing interference to licensed users. Reinforcement learning (RL), which is an artificial intelligence approach, has been applied to enable each unlicensed user to observe and carry out optimal actions for performance enhancement in a wide range of schemes in CR, such as dynamic channel selection and channel sensing. This paper presents new discussions of RL in the context of CR networks. It provides an extensive review on how most schemes have been approached using the traditional and enhanced RL algorithms through state, action, and reward representations. Examples of the enhancements on RL, which do not appear in the traditional RL approach, are rules and cooperative learning. This paper also reviews performance enhancements brought about by the RL algorithms and open issues. This paper aims to establish a foundation in order to spark new research interests in this area. Our discussion has been presented in a tutorial manner so that it is comprehensive to readers outside the specialty of RL and CR.
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