Discovering Utility-driven Interval Rules

For artificial intelligence, high-utility sequential rule mining (HUSRM) is a knowledge discovery method that can reveal the associations between events in the sequences. Recently, abundant methods have been proposed to discover high-utility sequence rules. However, the existing methods are all related to point-based sequences. Interval events that persist for some time are common. Traditional interval-event sequence knowledge discovery tasks mainly focus on pattern discovery, but patterns cannot reveal the correlation between interval events well. Moreover, the existing HUSRM algorithms cannot be directly applied to interval-event sequences since the relation in interval-event sequences is much more intricate than those in point-based sequences. In this work, we propose a utility-driven interval rule mining (UIRMiner) algorithm that can extract all utility-driven interval rules (UIRs) from the interval-event sequence database to solve the problem. In UIRMiner, we first introduce a numeric encoding relation representation, which can save much time on relation computation and storage on relation representation. Furthermore, to shrink the search space, we also propose a complement pruning strategy, which incorporates the utility upper bound with the relation. Finally, plentiful experiments implemented on both real-world and synthetic datasets verify that UIRMiner is an effective and efficient algorithm.Comment: Preprint. 11 figures, 5 table

QUASI-Three-Level Laser Emissions of Neodymium-Doped Disordered Crystal Waveguides

This paper reports on the quasi-three-level continuous wave laser operation based on waveguide structures in neodymium-doped calcium niobium gallium garnet disordered crystal. Laser wavelength selection through the waveguide cross section was observed. Waveguide structures with different cross sections were fabricated by the ultrafast laser inscription, which have propagation losses around 1 dB/cm. With suitable pumping conditions, laser emissions were observed at the low wavelengths of ~930 and ~890 nm. The lasing threshold for the low-wavelength emission was around 50 mW, which is far below the threshold of several watts reported in the bulk laser system. In addition, it was found that the laser generation at the wavelength of ~890 nm has direct relationship with the volume of the waveguide structure. The results suggest advantages of the waveguide platforms over the bulk systems on the low-wavelength laser emission

Tri-wavelength laser generation based on neodymium doped disordered crystal waveguide

[EN]We demonstrate a tri-wavelength laser generation from a Nd-doped calcium niobium gallium garnet disordered crystal waveguide. The laser threshold obtained was 83 mW of launched pumping laser corresponding to a slope efficiency of 5.1%. According to the laser spectrum, the output light was found to be a tri-wavelength laser, with wavelengths of 1058 nm, 1060 nm and 1064 nm, respectively. The stability of the output laser was investigated, which found that the output laser was a continuous laser.This work was carried out under the support by the National Natural Science Foundation of China (No. 11274203), the Spanish Ministerio de Ciencia e Innovación (projects CSD2007-00013 and FIS2009-09522), and the Junta de Castilla y León (project SA086A12-2). Yang Tan acknowledges the support by the Independent Innovation Foundation of Shandong University (IIFSDU, No. 104222012GN056 / 11160072614098) and China Postdoctoral Science Foundation (Grant No. 2013M530316)

Atomic-layer molybdenum sulfide optical modulator for visible coherent light

Coherent light sources in the visible range are playing important roles in our daily life and modern technology, since about 50% of the capability of the our human brains is devoted to processing visual information. Visible lasers can be achieved by nonlinear optical process of infrared lasers and direct lasing of gain materials, and the latter has advantages in the aspects of compactness, efficiency, simplicity, etc. However, due to lack of visible optical modulators, the directly generated visible lasers with only a gain material are constrained in continuous-wave operation. Here, we demonstrated the fabrication of a visible optical modulator and pulsed visible lasers based on atomic-layer molybdenum sulfide (MoS 2), a ultrathin two-dimensional material with about 9-10 layers. By employing the nonlinear absorption of the modulator, the pulsed orange, red and deep red lasers were directly generated. Besides, the present atomic-layer MoS 2 optical modulator has broadband modulating properties and advantages in the simple preparation process. The present results experimentally verify the theoretical prediction for the low-dimensional optoelectronic modulating devices in the visible wavelength region and may open an attractive avenue for removing a stumbling block for the further development of pulsed visible lasers

Nonlinear optical response of Au nanorods for broadband pulse modulation in bulk visible lasers

Due to the lack of suitable optical modulators, directly generated Pr3+- and Dy3+-doped bulk visible lasers are limited in the continuous-wave operation; yet, pulsed visible lasers are only sparingly reported recently. It has been theoretically predicated that Au nanorods could modulate the visible light operation, based on the nonlinear optical response of surface plasmon resonance. Here, we demonstrate the saturable absorption properties of Au nanorods in the visible region and experimentally realized the pulsed visible lasers over the spectral range of orange (605nm), red (639nm), and deep red (721nm) with Au nanorods as the optical modulator. We show that Au nanorods have a broad nonlinear optical response and can serve as a type of broadband, low-cost, and eco-friendly candidate for optical switchers in the visible region. Our work also advocates the promise of plasmonic nanostructures for the development of pulsed lasers and other plasmonic devices

Anisotropic thermal expansion of monoclinic potassium lutetium tungstate single crystals

The anisotropic thermal expansion of a single crystal of KLu WO4 2 KLuW , obtained by the top-seeded solution growth method, has been investigated over a wide temperature range 50– 600 °C . The linear thermal-expansion tensor has been determined and its principal X, Y, and Z axes are in the 705 , 010 , and 107 crystallographic directions, respectively. The principal thermal-expansion coefficients I, II, and III are 12.8 10−6, 7.8 10−6, and 22.2 10−6 K−1, respectively. The principal axis with maximum thermal expansion Z with III=22.2 10−6 is located at 10.37° from the c axis. In comparison with KGd WO4 2 and KYb WO4 2, the thermal-expansion anisotropy of KLuW is weaker and therefore optical-quality crystals are easier to obtain than with KGdW and KYbW from a thermal-expansion standpoint