Optical-magnetic (OM) bifunctional materials are of great interest for developing advanced multifunctional devices. [1][2][3][4] Conventional OM bifunctional materials are composites that are produced by coupling optical materials with magnetic ones. It is very difficult to realize an interaction between the optical and magnetic properties (e.g., tuning the optical properties using a magnetic field) in these conventional OM materials because of the separation of the optical and magnetic phases. On the other hand, producing materials with OM interactions would be valuable for developing advanced OM devices for high-accuracy communications, aircraft guidance, and magnetic field detection. [4][5][6][7] OM interactions depend mainly on the outermost electrons and thus, occur at the atomic scale. To achieve an OM interaction, a single-phase material should simultaneously have optical and magnetic properties to ensure the OM interaction occurs between atoms in the same crystal lattice, not at the interface between two separated phases with a high density of defects.Recent reports show that OM interactions can be simultaneously observed in single-crystal or single-phase materials by lanthanide (Ln) doping, for example, NaGd-F 4 :Yb 3+ ,Er 3+ [8, 9] and Gd 2 O 3 :Yb 3+ ,Er 3+ . [6,10] The host materials containing Gd 3+ ions have paramagnetic properties while the doped Er 3+ ions form luminescent centers. [6,[8][9][10] The luminescence of Er 3+ ions depends on their coordinated magnetic ion, Gd 3+ . Therefore, if the impact of the coordinating magnetic ions on their luminescent centers is strong enough, they should change the luminescence of these lanthanide-doped materials depending on the magnetic field.In comparison to Gd 2 O 3 , NaGdF 4 has a lower matrix phonon energy so that it generates a higher luminescent efficiency. [11] Moreover, for NaLnF 4 structures, heavy doping of other lanthanide ions does not usually generate precipitating phases. Considering its advantages, we chose NaGdF 4 as the host material to dope with the classic upconversion ionic pair, Yb 3+ /Er 3+ , which can convert low-energy infrared (IR) photons to higher-energy visible light. To adjust the OM properties, an Nd 3+ ion was introduced into the NaGd-

We are in the dawn of deep learning explosion for smartphones. To bridge the gap between research and practice, we present the first empirical study on 16,500 the most popular Android apps, demystifying how smartphone apps exploit deep learning in the wild. To this end, we build a new static tool that dissects apps and analyzes their deep learning functions. Our study answers threefold questions: what are the early adopter apps of deep learning, what do they use deep learning for, and how do their deep learning models look like. Our study has strong implications for app developers, smartphone vendors, and deep learning R&D. On one hand, our findings paint a promising picture of deep learning for smartphones, showing the prosperity of mobile deep learning frameworks as well as the prosperity of apps building their cores atop deep learning. On the other hand, our findings urge optimizations on deep learning models deployed on smartphones, protection of these models, and validation of research ideas on these models.

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A novel and high-performance four-element ultra-wideband (UWB) multiple-input multipleoutput (MIMO) antenna is proposed in the paper. The proposed antenna is designed by using a novel integration technology of the symmetric layout, orthogonal structure, four-directional staircase-shaped decoupling, and multi-slit and multi-slot techniques. The mutual couplings among the antenna elements are significantly reduced by introducing the symmetric orthogonal and separated four-directional staircaseshaped structure. Furthermore, the antenna size is effectively miniaturized, and its impedance bandwidth is broadened by using a two-sided symmetric layout, partial and defected ground structure, the decoupling structure, and multi-slot and multi-slit techniques. Therefore, the antenna has the low-profile structure and a small dimension of 39mm×39mm×1.6mm. Moreover, the proposed antenna achieves triple band-notched characteristics by embedding different type slots and slits on the square radiating elements, default ground structure, and the decoupling structure, respectively. As a result, the antenna obtains the wider bandwidth of 2.30-13.75 GHz with the notched bands of 3.25-3.75 GHz, 5.08-5.90 GHz, and 7.06-7.95 GHz. The three notched bands are good in agreement with the existing interference bands of WiMAX (3.3-3.7 GHz), , and X-band (7.1-7.9 GHz), respectively. In addition, the proposed antenna also has a lower mutual coupling (<−22dB), lower envelop correlation coefficient (ECC<0.02, except for the three notched bands), high multiplexing efficiency (η mux >−3.0dB), stable gain, and quasi-omnidirectional radiation patterns at the entire impedance bandwidth. Therefore, a good tradeoff of the performance is obtained for the proposed antenna. The proposed antenna can be a good candidate for UWB-MIMO wireless communication applications, and especially for portable UWB-MIMO systems.INDEX TERMS UWB-MIMO antenna, symmetric orthogonal structure, multi-slot-multi-slit, high isolation, triple band-notched characteristics. I. INTRODUCTION