Controlled assembly of poly(vinyl pyrrolidone) fibers through an electric-field-assisted electrospinning method

In this paper, we develop an effective electric-field-assisted electrospinning method for the controlled deposition of poly(vinyl pyrrolidone) fibers. The electric field distribution becomes uniform and convergent due to the introduction of a metal plate and a focusing aid into the conventional electrospinning setup. As a result, the bending instability is suppressed and the jet is restricted to moving to the collector along a straight line. Helical structure of fibers with lateral width of about 10 μm is formed and aligned on a rotating substrate. The morphology of helical fibers can also be effectively adjusted by varying the collecting velocity.     

Split-step cubic B-spline collocation methods for nonlinear Schrödinger equations in one,two, and three dimensions with Neumann boundary conditions

Numerical Algorithms - In this paper, split-step cubic B-spline collocation (SS3BC) schemes are constructed by combining the split-step approach with the cubic B-spline collocation (3BC) method for...     

Nanocrystals of CeVO4 doped by metallic heteroions

CeVO(4) nanocrystals doped by heteroions were prepared via a hydrothermal method without the presence of surfactants or templates. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), solid state (51)V NMR, and inductively coupled plasma (ICP) were used to characterize the morphology, structure, and compositions of the materials. X-ray photoelectron spectroscopy (XPS) results confirmed that there is a valence change from Ce(3+) to Ce(4+) for a fraction of cerium atoms whereas the vanadium atoms remain in the pentavalent state V(5+) upon the substitution of Ca(2+) into CeVO(4). Raman spectroscopy was used to monitor the effects of the doping ion on the CeVO(4) lattice contraction and distortion. The appearance of the shifted and broadened Raman peaks for the doped CeVO(4) was interpreted by theoretical calculations performed with Vienna ab initio simulation package. The redox properties and photocatalytic activities of the obtained nanocrystals were also investigated and discussed in detail.     

A new numerical scheme for the nonlinear Schrödinger equation with wave operator

In this paper, a new compact finite difference scheme is proposed for a periodic initial value problem of the nonlinear Schrödinger equation with wave operator. This is an explicit scheme of four levels with a discrete conservation law. The unconditional stability and convergence in maximum norm with order \(O(h^{4}+\tau ^{2})\) are verified by the energy method. Those theoretical results are proved by a numerical experiment and it is also verified that this scheme is better than the previous scheme via comparison.     

Conservative schemes for the symmetric Regularized Long Wave equations

In this paper, we study the Symmetric Regularized Long Wave (SRLW) equations by finite difference method. We design some numerical schemes which preserve the original conservative properties for the equations. The first scheme is two-level and nonlinear-implicit. Existence of its difference solutions are proved by Brouwer fixed point theorem. It is proved by the discrete energy method that the scheme is uniquely solvable, unconditionally stable and second-order convergent for U in L_∞ norm, and for N in L₂ norm on the basis of the priori estimates. The second scheme is three-level and linear-implicit. Its stability and second-order convergence are proved. Both of the two schemes are conservative so can be used for long time computation. However, they are coupled in computing so need more CPU time. Thus we propose another three-level linear scheme which is not only conservative but also uncoupled in computation, and give the numerical analysis on it. Numerical experiments demonstrate that the schemes are accurate and efficient.     

FAAS极限精确度法及其在金分析中的应用

本文介绍一种在火焰原子吸收光谱分析中提高测量精确度的方法－极限精确度法及其应用实例。     

An exponential wave integrator Fourier pseudospectral method for the nonlinear Schrödinger equation with wave operator

In this article, an exponential wave integrator Fourier pseudospectral (EWI-FP) method is proposed for solving the nonlinear Schrödinger equation with wave operator. The numerical method is based on a Deuflhard-type exponential wave integrator for temporal integration and the Fourier pseudospectral method for spatial discretizations. The scheme is fully explicit and very efficient thanks to the fast Fourier transform. Numerical analysis of the proposed EWI-FP method is carried out and rigorous error estimates are established by means of the mathematical induction. Numerical results are reported to confirm the theoretical studies.     

Linearly-Independent Quantum States Can Be Cloned by a Unitary-Reduct ion Operation

The famous quantum no-cloning theorem [Nature 299(1952)802] forbids replication of an arbitrary unknown quantum state. But it leaves open the follorc-ing question: If the state is not completely arbitrary, but secretly chosen from a certain set $ = {|Ψ₁>,| Ψ₂>,...,|Ψ_n>}, whether is the cloning possible? It is proved that the states from the set $ = {|Ψ₁>,| Ψ₂>,...,|Ψ_n>} can be faithfully cloned by a general unitary-reduction operation in a probabilistic fashion if and only if |Ψ₁>,| Ψ₂>,... and |Ψ_n> are linearly-independent.     

High resolution O MAS and triple-quantum MAS NMR studies of gallosilicate glasses

Gallosilicate (or ‘galliosilicate’) glasses have been widely studied as analogs of aluminosilicates, and the variations with composition in properties are known to be similar in both systems. We have applied ¹⁷O MAS and triple-quantum MAS (3QMAS) NMR spectroscopy to investigate the oxygen local environments in Na-, Li-, Ca- and Y-gallosilicate glasses. Signals due to several different oxygen species can be resolved and their concentrations quantified and NMR parameters determined. The NMR spectra generally resemble those of aluminosilicate glasses, indicating that the current model of gallium ions occupying the same types of sites as aluminum ions is a good first approximation. Quadrupolar coupling constants for the various oxygen sites tend to be larger than those for aluminosilicates, however, and vary less among different types of sites. Broader ¹⁷O spectra at low to medium external magnetic fields result. In detail, several types of differences between the observed oxygen species populations for gallosilicate and aluminosilicate are consistent with the larger radius of Ga³⁺ in comparison to Al³⁺, and possibly with a somewhat greater tendency for the former to form groups with oxygen coordination numbers greater than four. These include more Si-Ga disorder than Si-Al disorder in corresponding sodium gallo- vs. aluminosilicates, and more ‘non-stoichiometric’ non-bridging oxygen in a calcium gallosilicate than in a calcium aluminosilicate glass.