Thermal loading induced near-infrared broadband upconversion emission of Sm-doped β-NaYbF4 nano-phosphors

A non-closed hydrothermal synthetic processing is improved to synthesize Sm³⁺ doped β-NaYbF₄ nano-phosphors at 98 °C without any high-temperature and high-pressure treatments as a final step. Novel green, red, and near-infrared broadband (799-873 nm) upconversion emissions of Sm³⁺-doped β-NaYbF₄ nano-phosphors under 980 nm excitation are observed. These UC emissions can be assigned to the Sm³⁺ transitions of ⁴G_J, ⁴F_3/2 and ⁶F_11/2→⁶H_J. The half-width of 873 nm emission band is broadened nearly two-fold through the annealing treatment for nano-phosphors. The upconversion process in Yb³⁺-Sm³⁺ system is discussed based on energy transfer mechanisms.     

Properties of a vector soliton laser passively mode-locked by a fiber-based semiconductor saturable absorber operating in transmission

We experimentally demonstrate a passively mode-locked fiber laser employing a fiber-based semiconductor saturable absorber (SSA) operating in transmission. Polarization rotation locked vector solitons are observed in the laser. Due to the intrinsic dynamic feature of the laser, period-doubling of these vector solitons has also been observed. Furthermore, extra spectral sidebands are formed on the optical spectrum, caused by the energy exchange between the two orthogonal polarization components of the vector solitons. By careful reduction of the pump power together with fine adjustment to the cavity birefringence, period-one state can further be obtained. Additionally, the phase noise properties of the vector soliton fiber laser have also been characterized experimentally and analytically.     

General theory for the ferroelectric polarization induced by spin-spiral order

The ferroelectric polarization of triangular-lattice antiferromagnets induced by helical spin-spiral order is not explained by any existing model of magnetic-order-driven ferroelectricity. We resolve this problem by developing a general theory for the ferroelectric polarization induced by spin-spiral order and then by evaluating the coefficients needed to specify the general theory on the basis of density functional calculations. Our theory correctly describes the ferroelectricity of triangular-lattice antiferromagnets driven by helical spin-spiral order and incorporates known models of magnetic-order-driven ferroelectricity as special cases.     

Comparison of catalytic activities for photocatalytic and sonocatalytic degradation of methylene blue in present of anatase TiO2-CNT catalysts

Anatase TiO(2)-CNT catalysts with high specific surface areas were prepared by depositing TiO(2) particles on the surface of carbon nanotubes (CNTs) using a modified sol-gel technique. These catalysts prepared with different amounts of CNTs were characterized by nitrogen adsorption, Fourier Transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), Raman spectroscopy, energy dispersive X-ray (EDX) and ultraviolet-visible (UV-Vis) spectroscopy. The catalytic activity of the anatase TiO(2)-CNT catalysts was assessed by examining the degradation of methylene blue (MB) from model aqueous solutions as a probe reaction under visible light and ultrasonic irradiation. The synergistic effect of the greater surface area and catalytic activities of the composite catalysts was examined in terms of the strong adsorption ability and interphase interaction by comparing the different amounts and roles of CNTs in the catalysts.     

Density functional predictions of new silicon allotropes: Electronic properties and potential applications to Li-battery anode materials

In terms of first-principles density functional calculations, we investigate the stabilities and electronic properties of two hypothetical allotropes of silicon, the body-centered tetragonal (Bct) and monoclinic (M4) phases. The calculated electronic structures and phonon dispersions reveal that both phases are stable and have a band gap smaller than that of the diamond form of silicon by a factor of ∼2. We also discuss the possible applications of Bct and M4 phases as lithium-battery anode material.     

Taxonomy of batch queueing models in manufacturing systems

Batching plays an important role in performance evaluation of manufacturing systems. Three types of batching are commonly seen: transfer batches, parallel batches and serial batches. To model the batching behavior correctly, a comprehensive classification of batching is proposed. Eight types of batching behavior are classified and corresponding queueing models are given. The newly proposed models are validated by simulation.     

Separation and determination of lignans from seeds of Schisandra species by micellar electrokinetic capillary chromatography using ionic liquid as modifier

In this paper, a micellar electrokinetic chromatographic (MEKC) method using ionic liquid as modifier for the quantification of the active components of lignans found in the medicinal herbs Schisandra species was developed for the first time. Preliminary investigations employing sodium dodecyl sulfate (SDS) as surfactant did not lead to the necessary resolution of the studied compounds, the addition of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4) to the SDS micellar system resulted in the complete separation of all the compounds. The effects on the separation by several parameters such as BMIM-BF4 and SDS concentration, applied voltage, background electrolyte pH and concentration, were evaluated. Under the optimal conditions (5 mM borate-5 mM phosphate buffer in the presence of 20 mM SDS and 10 mM BMIM-BF4, pH 9.2, applied voltage 25 kV and detection at 254 nm), the method successfully applied to the determination of lignans in extracts of Schisandra chinensis (Turcz.) Baill. and Schisandra henryi C.B. Clarke in less than 13 min. The separation mechanism was also discussed.