Structural and thermodynamic properties of Os from first-principles calculations

We investigate the structural, thermodynamic and electronic properties of Os by plane-wave pseudopotential density functional theory method. The obtained lattice constants, bulk modulus and cell volumes per formula unit are well consistent with the available experimental data. Especially, from our calculated bulk modulus, we conclude that Os is more compressible than diamond. Moreover, the temperature induced phase transition of Os from HCP structure to FCC structure has been obtained. It is found that the transition temperature of Os at zero pressure is 2702 K. However no transition pressure is found in our calculations. The effect of bulk modulus B as well as other thermodynamic properties of Os (including the thermal expansion α and the Grüneisen constant γ) on temperatures have also been studied. Our calculated thermal expansion α=1.510×10⁻⁵ K⁻¹ and the Grüneisen constant γ=2.227 for HCP structure at room temperature agree very well with the experimental data. The density of states for HCP structure at 0 K and FCC structure at transition temperature 2702 K are also investigated in our work.     

Numerical simulation of turbulent combustion: Scientific challenges

Predictive simulation of engine combustion is key to understanding the underlying complicated physicochemical processes, improving engine performance, and reducing pollutant emissions. Critical issues as turbulence modeling, turbulence-chemistry interaction, and accommodation of detailed chemical kinetics in complex flows remain challenging and essential for high-fidelity combustion simulation. This paper reviews the current status of the state-of-the-art large eddy simulation (LES)/prob-ability density function (PDF)/detailed chemistry approach that can address the three challenging modelling issues. PDF as a subgrid model for LES is formulated and the hybrid mesh-particle method for LES/PDF simulations is described. Then the development need in micro-mixing models for the PDF simulations of turbulent premixed combustion is identified. Finally the different acceleration methods for detailed chemistry are reviewed and a combined strategy is proposed for further development.     

Effects of humic acids and microorganisms on decabromodiphenyl ether, 4,4′-dibromodiphenyl ether and anthracene transportation in soil

In this study, effects of humic acids (HA) and microorganisms on the migration of hydrophobic organic contaminants (HOCs), decabromodiphenyl ether (BDE-209), 4,4′-dibromodiphenyl ether (BDE-15) and anthracene, in soils were examined. More soil particles were dispersed into the colloidal phase (0.22-1 μm) in the presence of HA and/or microorganisms as a result of increased erosion and friction. The study suggested that PBDEs (BDE-209 and BDE-15) and anthracene in soils would be transported to other places by...     

1-苯基-3-甲基-4-苯甲酰基吡唑啉酮/PdCl2在温和条件下催化Suzuki偶联反应的研究

考察了商品化的简单非膦配体1-苯基-3-甲基-4-苯甲酰基吡唑啉酮在有氧温和条件下的Suzuki偶联反应活性,探讨了反应温度、反应时间、溶剂以及碱对反应的影响。结果表明,该配体在优化的反应条件下能高效催化不同溴代反应物和氯代反应物与苯硼酸的交叉偶联反应;提高反应温度、延长反应时间和引入质子性极性有机/水混合溶剂有利于偶联反应的进行。     

Chiral-glass transition in a diluted dipolar-interaction Heisenberg system

Recently, numerical simulations reveal that a spin-glass transition can occur in the three-dimensional diluted dipolar system. By defining the chirality of triple spins in a diluted dipolar Heisenberg spin glass, we study the chiral ordering in the system using parallel tempering algorithm and heat bath method. The finite-size scaling analysis reveals that the system undergoes a chiral-glass transition at finite temperature.     

Triple Wronskian solutions of the coupled derivative nonlinear Schrödinger equations in optical fibers

A type of the coupled derivative nonlinear Schrödinger (CDNLS) equations are studied by means of symbolic computation, which can describe the wave propagation in birefringent optical fibers. Soliton solutions in the triple Wronskian form of the CDNLS equations are obtained. Elastic and inelastic collisions are both presented under some parametric conditions. In addition, generalized triple Wronskian solutions of a set of the coupled general derivative nonlinear Schrödinger (CGDNLS) equations are derived. Triple Wronskian identities are given to prove such solutions, which may also be used for other coupled nonlinear equations. Rational solutions of the CGDNLS equations are also obtained.     

Synthesis of submicron rhombic ZnO rods via ZnOHF intermediate using electrodeposition route

ZnOHF submicron rods with the rhombus-like shape were successfully prepared by a low-temperature aqueous electrodeposition route. By further adjusting the experimental parameters including the electrolyte concentration, temperature, the electrodeposition potential, and the duration, the morphologies of ZnOHF films can further be controlled; accordingly, ZnO films with different morphologies were also obtained by calcining ZnOHF intermediate at 400 °C for 2 h. Based on the experimental results, a plausible mechanism for the conversion from ZnOHF to ZnO crystals was proposed. The surface morphology and microstructure of the products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the optical property of the samples was investigated by room-temperature photoluminescence (PL) spectra as well. The PL spectra confirmed that ZnOHF and ZnO exhibited emission band centered at 413 nm and 382 nm in UV region, respectively.     

Breather and double-pole solutions of the derivative nonlinear Schrödinger equation from optical fibers

The derivative nonlinear Schrödinger (DNLS) equation, which governs the propagation of the femtosecond optical pulse in a monomodal optical fiber, is analytically studied in this Letter. Breather and double-pole solutions are derived from the two-soliton solution with the choice of parameters. It is found that the parameters in the DNLS equation cannot only control the phase and propagation direction of the breather and double pole, but also influence the interaction period of the breather. Elastic collisions between a breather and a dark/anti-dark soliton are studied by the qualitative analysis and graphical illustration. The stability of the breather and double-pole solutions is also analyzed.