Dynamics of solvated electron transfer in thin ice film leading to a large enhancement in photodissociation of CFCl3

Solvation and transfer dynamics of photoinjected electrons in thin ice film coadsorbed with CFCl3 were investigated by two-photon photoemission spectroscopy. Water molecules were found to solvate the photoinjected electrons within the first several hundred femtoseconds, thus stabilizing the electron with a lifetime of ca. 120 fs for 5 ML ice film grown on Ag(111). The significant lifetime decrease upon adsorption of CFCl3 on the ice film was attributed to dissociative electron transfer of the solvated electron based on the observed scission of the C-Cl bonds. Furthermore, the photodissociation rate of CFCl3 adsorbed directly on Ag(111) was observed to increase drastically owing to the transfer of the solvated electron when ice film was overlaid.     

Phase conversion of chemically exfoliated molybdenum disulfide

Multilayer MoS₂ is exfoliated by Li treatment. A thin film of Li-treated MoS₂ contains a large portion of 1T phases. This is attributed to the atomic structural change caused by Li insertion, which is investigated using X-ray photoelectron spectroscopy (XPS). In a phase recovery via thermal annealing at 523 K in air, we observe another phase, referred to as the relaxed 1T phase, with a slightly larger binding energy than the 1T phase. After annealing at 523 K in air, the peak intensity of the relaxed 1T phase is reduced, accompanying a strong MoO_x peak and weak S 2s peak, according to XPS. This indicates that the annealing of Li-treated MoS₂ in air yields sulfur vacancies that induce the oxidation of Mo. However, after annealing at 523 K in vacuum, no MoO_x is observed, and the considerable peak intensity of the relaxed 1T phase remains, which starkly contrasts Raman-spectroscopy results supporting a full recovery from the 1T phase to the 2H phase. The absence of a gating effect of the Li-treated MoS₂ device supports the possibility of an incomplete phase change of Li-treated MoS₂ annealed in a vacuum.     

Performance evaluation of electronic control suspension featuring vehicle ER dampers

This paper presents ride comfort and driving stability performances of electronic control suspension (ECS) equipped with controllable electrorheological (ER) damper and appropriate control strategy. In order to achieve this goal, a cylindrical type ER damper which is applicable to Macpherson strut type suspension of a mid-sized passenger vehicle is designed and manufactured on the basis of the required damping force level of an existing passenger vehicle. After experimentally evaluating the field-dependent damping force and dynamic characteristics of the controllable ER damper, ECS consisting of sprung mass, spring, tire and controller is established in order to investigate the ride comfort and driving stability performances. On the basis of the governing equation of motion of the suspension system, five control strategies (soft, hard, comfort, sports and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in both time and frequency domains under various road conditions. In addition, a comparative work is undertaken to investigate inherent control characteristics of each control strategy.     

The effect of nonlinearity on unstable zones of Mathieu equation

Mathieu equation is a well-known ordinary differential equation in which the excitation term appears as the non-constant coefficient. The mathematical modelling of many dynamic systems leads to Mathieu equation. The determination of the locus of unstable zone is important for the control of dynamic systems. In this paper, the stable and unstable regions of Mathieu equation are determined for three cases of linear and nonlinear equations using the homotopy perturbation method. The effect of nonlinearity is examined in the unstable zone. The results show that the transition curves of linear Mathieu equation depend on the frequency of the excitation term. However, for nonlinear equations, the curves depend also on initial conditions. In addition, increasing the amplitude of response leads to an increase in the unstable zone.     

Markedly enhanced recyclability of osmium catalyst in asymmetric dihydroxylation reactions by using macroporous resins bearing both residual vinyl groups and quaternary ammonium moieties

Markedly enhanced recyclability of osmium catalyst in asymmetric dihydroxylation has been achieved by using osmylated macroporous resins bearing both residual vinyl groups and quaternary ammonium moiety.     

Scaling behavior of mixed-state hall effect in MgB2 thin films

The Hall resistivity (ρ_xy) and the longitudinal resistivity (ρ_xx) in c-axis-oriented superconducting MgB₂ thin films have been investigated in extended fields up to 18 T. We have observed a scaling behavior between the Hall resistivity and the longitudinal resistivity, , where the exponent (β) is observed to be independent of the temperatures and the magnetic fields. For a wide magnetic field region from 1 to 18 T and a wide temperature region from 10 to 28 K, a universal power law with β = 2.0 ± 0.1 was observed in c-axis-oriented MgB₂ thin films. These results can be well interpreted by using recent models.     

On-line measurement of the RMS radius of gyration and molecular weight of polyimide precursor fractions eluting from a size-exclusion chromatograph

The recent introduction of multiangle light-scattering detectors for size-exclusion chromatography has made possible the measurement of the root mean square radius of gyration (R_g) and molecular weight (M) of polymer fractions eluting from a size-exclusion chromatography column. The characterization of the dimensions of a polymer may be accomplished with only a few milligrams. The dimensions of a polyimide precursor prepared by the condensation of the meta-diethyl ester of pyromellitic dianhydride with para-phenylene diamine have been measured with this technique. The dependence of R_g on M across the distribution is compared with that predicted for a freely rotating chain, and with other similar polymers measured with hydrodynamic techniques.     

Enhancement of red spectral emission intensity of Y3Al5O12:Ce phosphor via Pr co-doping and Tb substitution for the application to white LEDs

We have enhanced color-rendering property of a blue light emitting diode (LED) pumped white LED with yellow emitting Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce) phosphor using addition of Pr and Tb as a co-activator and host lattice element, respectively. Pr³⁺ addition to YAG:Ce phosphor resulted in sharp emission peak at about 610 nm through ¹D₂→³H₄ transition. And when Tb³⁺ substituted Y³⁺ sites, Ce³⁺ emission band shifted to a longer wavelength due to larger crystal field splitting. Y₃Al₅O₁₂:Ce³⁺, Pr³⁺ and (Y_1−xTb_x)₃Al₅O₁₂:Ce³⁺ phosphors were coated on blue LEDs to fabricate white LEDs, respectively, and their color-rendering indices (CRIs, R_a) were measured. As a consequence of the addition of Pr³⁺ or Tb³⁺, CRI of the white LEDs improved to be R_a=83 and 80, respectively. Especially, blue LED pumped (Y_0.2Tb_0.8)₃Al₅O₁₂:Ce³⁺ white LED showed both strong luminescence and high color-rendering property.     

Hybrid weighted-density approximation for nonuniform fluid mixtures

A hybrid weighted-density approximation (HWDA), which is based on both local density and globally averaged density, has been proposed to study the structural properties of nonuniform fluid mixtures. The advantage is that the HWDA is computationally much simpler than the extended weighted-density approximation proposed by Davidchack and Laird. The HWDA has been applied to calculate the density profiles of binary hard-sphere mixtures near a structureless hard wall. Comparison between the theoretical results and simulations for the confined binary hard-sphere mixtures demonstrates the reliable accuracy of the HWDA.     

Strong upconversion–downshifting green emission from Tb<Superscript>3+</Superscript> ions in core/shell/shell-structured nanophosphors

Efficient upconversion (UC)–downshifting (DS), dual-mode-emitting NaGdF₄:Yb,Tm/NaGdF₄:Tb/NaYF₄ core/shell/shell (C/S/S) nanophosphors (NPs) were synthesized. The UC luminescence color changed from blue to sky blue after doping Tb³⁺ into NaGdF₄ shell because Tb³⁺ emission peaks via ⁵D₄ → ⁷F_J transition were observed with Tm³⁺ emission peaks via ¹D₂ → ³F₄ and ¹G₄ → ³H₆ transitions through the energy migration UC process of Yb³⁺ → Tm³⁺ → Gd³⁺ → Tb³⁺. Upon increasing the Tb³⁺ concentration in the NaGdF₄ shell from 5 to 15%, the Commission Internationale de l’Éclairage (CIE) color coordinates changed from (0.2188, 0.2390) to (0.2616, 0.3654). When NaGdF₄:Yb(49%),Tm(1%)/NaGdF₄:Tb(15%)/NaYF₄ NPs were excited using 273 nm ultraviolet light, the C/S/S NPs exhibited bright green light with CIE color coordinates of (0.3354, 0.5090) as a result of energy transfer from Gd³⁺ to Tb³⁺. These bright UC–DS, dual-mode-emitting C/S/S NPs could be applied in various applications, including multiplexed imaging and anticounterfeiting.