Efficiency improvement of InGaP/GaAs/Ge solar cells by hydrothermal-deposited ZnO nanotube structure

In this paper, a zinc oxide (ZnO) nanotube, fabricated by the hydrothermal growth method on triple-junction (T-J) solar cell devices to enhance efficiency, is investigated. Compared to those of bare T-J solar cells (without antireflection (AR) coating) and solar cells with Si₃N₄ AR coatings, the experimental results show that the T-J solar cells, which use a ZnO nanotube as an AR coating, have the lowest reflectance in the short wavelength spectrum. The ZnO nanotube has the lowest light reflection among all experimental samples, especially in the range of 350 to 500 nm from ultraviolet (UV) to visible light. It was found that a ZnO nanotube can enhance the conversion efficiency by 4.9%, compared with a conventional T-J solar cell. The Si₃N₄ AR coatings also enhance the conversion efficiency by 3.2%.The results show that a cell with ZnO nanotube coating could greatly improve solar cell performances.     

Synthesis of highly concentrated suspension of chemically converted graphene in organic solvents: Effect of temperature on the extent of reduction and dispersibility

We report the effect of temperature on the extent of graphene oxide reduction by hydrazine and the dispersibility of the resulting chemically converted graphene (CCG) in polar organic solvents. The extent of graphene oxide reduction at high temperatures was only slightly higher than at low temperatures (30–50 °C), while the dispersibility of the resulting CCG in organic solvents decreased markedly with increasing temperature. The low dispersibility of CCGs prepared at high temperatures was greatly affected by reduction and influenced by the formation of an irreversible agglomerate of CCG at high temperatures. The reduction of graphene oxide at low temperatures is necessary to prepare highly dispersible CCG in organic solvents. CCG prepared at 30 °C is dispersible in N-methyl-2-pyrrolidone concentrations as high as 0.71 mg/mL. The free-standing paper made of this CCG possessed an electrical conductivity of more than 22,000 S/m, one of the highest values ever reported.     

A numerical scheme based on compact integrated-RBFs and Adams–Bashforth/Crank–Nicolson algorithms for diffusion and unsteady fluid flow problems

This paper presents a high-order approximation scheme based on compact integrated radial basis function (CIRBF) stencils and second-order Adams–Bashforth/Crank–Nicolson algorithms for solving time-dependent problems in one and two space dimensions. We employ CIRBF stencils, where the RBF approximations are locally constructed through integration and expressed in terms of nodal values of the function and its derivatives, to discretise the spatial derivatives in the governing equation. We adopt the Adams–Bashforth and Crank–Nicolson algorithms, which are second-order accurate, to discretise the temporal derivatives. The performance of the proposed scheme is investigated numerically through the solution of several test problems, including heat transfer governed by the diffusion equation, shock wave propagation and shock-like solution governed by the Burgers' equation, and torsionally oscillating lid-driven cavity flow governed by the Navier–Stokes equation in the primitive variables. Numerical experiments show that the proposed scheme is stable and high-order accurate in reference to the exact solution of analytic test problems and achieves a good agreement with published results for other test problems.     

Synthesis and characterization of the carbon nanotube-based composite materials with poly(3,4-ethylenedioxythiophene)

We report a procedure to prepare a conducting nano-composites composed of multi-walled carbon nanotubes (MWNTs) and PEDOT by using a poly(sodium 4-styrenesulfonate) (PSSNa) as a inter-linking molecule between MWNT and PEDOT. When PSSNa chains are introduced on the MWNTs via physicochemical interaction, the surface of MWNT becomes negatively charged, and PSS-modified MWNTs promote the effective association of the positively charged PEDOT chains. The resulting MWNT-PSS/PEDOT composites are characterized by a better interconnection between MWNT and PEDOT components.     

Extended finite element method for plastic limit load computation of cracked structures

The extended finite element method is extended to allow computation of the limit load of cracked structures. In the paper, it is demonstrated that the linear elastic tip enrichment basis with and without radial term may be used in the framework of limit analysis, but the six‐function enrichment basis based on the well‐known Hutchinson–Rice–Rosengren asymptotic fields appears to be the best. The discrete kinematic formulation is cast in the form of a second‐order cone problem, which can be solved using highly efficient interior‐point solvers. Finally, the proposed numerical procedure is applied to various benchmark problems, showing that the present results are in good agreement with those in the literature. Copyright © 2015 John Wiley & Sons, Ltd.