Simulation of atomic and ionic absorption and emission spectra for thermal plasma diagnostics: application to a volatilisation study in a plasma jet

Simulation of atomic emission and absorption spectra has been carried out in order to improve and to check the validity of measurement techniques and data processing for plasma diagnostic. Doppler, Van der Waals, Stark and instrumental broadenings and shifts have been taken into account. The effect of self-absorption has also been considered. The input parameters are pressure, temperature, electron density, and emitting species number density. In such calculations data needed for the determination of collisional and Stark broadenings are not always available. An empirical method of data evaluation is described and discussed. The limits and the precision of this modelling are discussed with experimental examples. This simulation method has been applied to the diagnostic of volatilisation phenomena in thermal plasma spraying processes. It has been used to assist in the choice of diagnostic lines, instrumental parameters and data processing parameters. It has also been used to evaluate the accuracy of the temperature and density distributions calculated from spectroscopic measurements.     

Structural Equation and Mei Conserved Quantity of Mei Symmetry for Appell Equations in Holonomic Systems with Unilateral Constraints

Structural equation and Mei conserved quantity of Mei symmetry for Appell equations in holonomic systems with unilateral constraints are investigated. Appell equations and differential equations of motion for holonomie mechanic systems with unilateral constraints axe established. The definition and the criterion of Mei symmetry for Appell equations in holonomic systems with unilateral constraints under the infinitesimal transformations of groups axe also given. The expressions of the structural equation and Mei conserved quantity of Mei symmetry for Appell equations in holonomic systems with unilateral constraints expressed by Appell functions are obtained. An example is given to illustrate the application of the results.     

Entanglement dynamics and Bell violation of three-qubit states coupled to an XY spin chain with Dzyaloshinski–Moriya interaction

We investigate the entanglement dynamics and Bell violation of three-qubit quantum states under an environment consisting of an XY spin chain with Dzyaloshinski–Moriya (DM) interaction. From the results, we find that the entanglement dynamics depends not only on the DM interaction, the magnetic field, and the anisotropy parameter but also on the number of the freedom degrees of the environment. The decoherence-free subspaces of our model have been identified and the Bell violation of quantum states is also discussed.     

Inelastic partial cross sections for scattering of HF by neon

An analytic expression of the potential energy surface (PES) of the ground state of the Ne-HF complex is obtained by utilizing nonlinear least square method to fit the intermolecular interaction energies [Zhang Y. Guizhou Science, 2003, 21(3): 9–13 (in Chinese)], which have been computed using the augmented correlation-consistent polarized quadruple zeta basis set aug-cc-pVQZ at the theoretical level of CCSD (T). On the basis of the PES, the partial cross sections (PCSs) at the incident energies of 60, 75, 100 and 150 meV for collisions between Ne atoms and HF molecules are calculated using the quantum close coupling approach. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic PCSs are discussed in detail. The results show: (1) The long-range attractive well of the EPS makes the significant contribution to the lower excitation PCSs, especially the tail maximum for j = 0→j′ = 1 transitions, whereas no contribution is to the j′⩾3 inelastic transitions. (2) The short-range (the repulsive and attractive) interaction makes the significant contribution to the lower excitation PCSs, especially the main peak for j = 0→j′ = 1, 2. As for the transitions of j′⩾3, the short-range interaction plays a key role in the inelastic excitation. (3) Although the positions of the maximums and minimums of the inelastic PCSs are different at the collision energies, they correspond to almost the same impact parameter. Supported by the National Natural Science Foundation of China (Grant Nos. 10676025 and 10574096)     

Molar volumes and viscosities of LiClO4 and LiBr in propylene carbonate + 1,2-dimethoxyethane mixed solvents at 298.15 K

The standard partial molar volumes, viscosity B-coefficients and activation free energies of lithium salts (LiClO₄ and LiBr) in propylene carbonate (PC) with 1,2-dimethoxyethane (DME) mixed solvents have been determined as a function of the mole fraction of DME at 298.15 K from precise density and viscosity measurements. The values studied are all positive and decrease monotonously with addition of DME in the PC, which indicates that nature of the solvents plays an important role. The effects are discussed in terms of preferential solvation and packing effect in the solvation shell and electrostriction. The differences between ClO₄⁻ and Br⁻ have also been discussed.     

Two-dimensional TiO2 (001) nanosheets as an effective photo-assisted recyclable sensor for the electrochemical detection of bisphenol A

Electrochemical detection is an efficient method for the detection of Bisphenol A (BPA). Herein, a sensitive photo-electrochemical sensor based on two-dimensional (2D) TiO₂ (001) nanosheets was fabricated and then used for BPA electrochemical detection. Upon light irradiation, the 2D TiO₂ (001) nanosheets electrode provided a lower detection limit of BPA detection compared with an ambient electrochemical determination. The low detection limit is ∼5.37 nmol/L (S/N = 3). Furthermore, profiting from the photoelectric characteristics, the 2D TiO₂ (001) nanosheets electrode exhibits a nice regeneration property. After 45 min of light irradiation, the electrochemical signal was regenerated from 14.7% to 82.9% of the original signal at the 6^th cycle. This is attributed to the non-selective OH mediation produced by the 2D TiO₂ (001) nanosheets mineralizing anodic polymeric products and resuming surface reactive sites. This investigation indicates that photo-assistance is an efficient method to improve the electrochemical sensor for detecting BPA in water environments.     

Synthesis,crystal chemistry and physical study of a new series of rare earth phosphates with specific open structure

Hexagonal rare earth phosphates with the composition LnP0₄,xKOH (Ln = Eu - Lu, Y; 0 < x ≤ 1), were prepared by coprecipitation of rare earth nitrates and potassium phosphate in basic medium. These compounds were characterized by X-ray diffraction and chemical analysis. The best crystallinity was obtained for samples heat-treated at 660–750°C in air during 24 h, in which the K content was determined to be near 1 % (wt). A Rietveld refinement of these hexagonal orthophosphates was performed in the same conditions as used for the hexagonal holmium orthophosphate reported earlier by us (rhabdophane-type, space group P6₂22). It indicated that a part of KOH is incorporated in the hexagonal form and that the other part remains in an amorphous form. Between 800 and 1200°C the two forms gradually transform into a zircon-type LnP0₄ phase for Ln = Tb-Lu, Y and a monazite-type LnP0₄ phase for Ln = Eu, Gd. The infrared spectra for all these compounds were obtained by the KBr disk method.     

The construction of boundary analogues of variational methods to approximate weak solutions of boundary-value problems in the theory of elasticity

Methods of approximating weak solutions of certain boundary-value problems in the theory of elasticity are proposed based on expanding the approximate solution in a finite series in basis functions which identically satisfy a homogeneous differential equation in the domain. The coefficients of the expansion are found by constructing a boundary analogue of the method of least squares (BAMLS). It is proved that the approximate solution thus obtained converges to a weak solution of the problem. Sufficient conditions for the stability of the BAMLS, easily verifiable by computational means, are derived. The construction of a boundary analogue of the collocation method (BACM) is proposed on the basis of the BAMLS, combined with discretization of the scalar product by quadrature formulae. The BACM obtained is convergent and stable and possesses better computational properties than the BAMLS.