Yannan Qian

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Feature selection for logistic regression (LR) is still a challenging subject. In this paper, we present a new feature selection method for logistic regression based on a combination of the zero-norm and l 2-norm regularization. However, discontinuity of the zero-norm makes it difficult to find the optimal solution. We apply a proper nonconvex approximation(More)
Ho3+/Yb3+/Tm3+ tridoped LiNbO3 single crystal exhibiting intense upconversion white light under 980 nm excitation has been successfully fabricated by the Czochralski method. The tridoped LiNbO3 single crystal offers power dependent color tuning properties by simply changing excitation power. Efficient three-photon blue upconversion emission and two-photon(More)
Codoping with Zr(4+) ions enhances the 1.54 μm emission in Yb/Er:LiNbO(3) crystal by about three times. Optical damage resistant Zr(4+) ion increases the maximum phonon energy of Er:LiNbO(3) host, which is favorable for the nonradiative relaxation from (4)I(11/2) to (4)I(13/2) state (Er). The time decay spectra show that the incorporation of Zr(4+) ions(More)
To increase the photovoltaic efficiency of solar cells, green and red upconversion (UC) emissions produced at an excitation of 1550 nm were investigated. A drastically enhanced red UC emission was observed in near-stoichiometric LiNbO(3) crystal heavily doped with Er(3+) ions (Er:NSLN). Raman spectra showed that the maximum phonon energy shifted from 631(More)
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