Phase transition in the one-dimensional pair-hopping model with unusual one-electron hopping

By modifying the conventional one-electron hopping behavior, we study effects of an occupation-dependent hopping on the ground state of the half-filled one-dimensional pair-hopping model. At weak coupling, the use of bosonization and renormalization-group analysis techniques helps to derive the phase diagram. Such unusual hopping is shown to drive a spin-gap transition and to introduce a new region where the triplet superconducting instability dominates for positively small pair-hopping interaction.     

Defects related emission and nanosecond optical power limiting in CuS quantum dots

We report optical and nonlinear optical properties of CuS quantum dots and nanoparticles prepared through a nontoxic, green, one-pot synthesis method. The presence of surface states and defects in the quantum dots are evident from the luminescent behavior and enhanced nonlinear optical properties measured using the open aperture Z-scan, employing 5 ns laser pulses at 532 nm. The quantum dots exhibit large effective third order nonlinear optical coefficients with a relatively lower optical limiting threshold of 2.3 J cm⁻², and the optical nonlinearity arises largely from absorption saturation and excited state absorption. Results suggest that these materials are potential candidates for designing efficient optical limiters with applications in laser safety devices.     

Investigation of Galilean invariance of multi-phase lattice Boltzmann methods

We examine the Galilean invariance of standard lattice Boltzmann methods for two-phase fluids. We show that the known Galilean invariant term that is cubic in the velocities, and is usually neglected, is a major source of Galilean invariance violations. We show that incorporating a correction term can improve the Galilean invariance of the method by up to two orders of magnitude for large velocities. We found that this is true in particular for methods in which the interactions are incorporated through a forcing term. Methods in which interactions are incorporated through a non-ideal pressure tensor only benefit for large velocities.     

Synchronization of complex dynamical networks with time delays

In the present paper, two kinds of dynamical complex networks are considered. The first is that elements of every node have different time delays but all nodes in such networks have the same time-delay vector. The second is that different nodes have different time-delay vectors, and the elements of each node also have different time delays. Corresponding synchronization theorems are established. Numerical examples show the efficiency of the derived theorems.     

Comparison between smoothed dissipative particle dynamics and Voronoi fluid particle model in a shear stationary flow

We present a numerical comparison between two Lagrangian techniques for the simulation of fluids, smoothed dissipative particle dynamics (SDPD) and Voronoi fluid particle model. These methods reproduce the movement of the fluid with extensive particles. The main differences between these techniques are the volume definition and the implementation of the second derivatives. The Voronoi model is computationally more efficient than SDPD. For quasi-regular meshes, the Voronoi method is more accurate than SDPD but for arbitrary configurations its precision degrades. This means that the SDPD discrete versions of the second derivative operators are better than the ones used in the Voronoi method.     

The enhancement of photoluminescence of n-type porous silicon by Hall-effect assistance during electrochemical anodization

In this study, n-type porous silicon (n-PS) films with high-aspect-ratio Si-tips are formed with the assistance of Hall-effect during the electrochemical anodization. Lorentz force sweeps down the majority carriers (electrons) in n-type Si to enhance the anodization etching. Surface layers are inverted from n-type to p-type, so sufficient holes can continuously appear on the surface to participate in chemical reaction during the etching process. Illumination is not necessary in this process, so the problem of illumination-depth limitation is solved. The etching current, morphology, and photoluminescence of the n-PS prepared in this way are investigated. Strong visible photoluminescence emissions at room temperature are demonstrated on n-PS.     

Multisplitting Iteration Schemes for Solving a Class of Nonlinear Complementarity Problems

We consider several synchronous and asynchronous multisplitting iteration schemes for solving aclass of nonlinear complementarity problems with the system matrix being an H-matrix.We establish theconvergence theorems for the schemes.The numerical experiments show that the schemes are efficient forsolving the class of nonlinear complementarity problems.     

两类拟共形映射的掩盖定理

In this paper we define two classes of quasiconformal mappings,and study their covering properties by methods of module.We obtain some new results.In the meantime,we give new methods to prove Koebe 1/2 covering theorem on convex conformal mappings.     

接枝羧基的有限长碳纳米管电子结构的第一性原理研究

基于局域密度泛函理论，采用第一性原理方法，建立了对(5,5)型和(9,0)型有限长碳纳米管接枝羧基官能团的原子模型，通过计算其电子分布和态密度的变化，讨论羧基官能团对碳纳米管电子结构和电子输运特性的影响. 计算表明，接枝羧基的碳纳米管,其电子结构明显改变，其费米能级上的电子态密度下降；最高占据轨道上的非定域程度减弱,致使电子输运性能呈下降趋势. 关键词： 碳纳米管 密度泛函理论 电子结构