Preparation and Characterization of Nanosized CeO2/γ-Al2O3 Composite Supports

Based on the γ-Al2O3 support with large-size pores, impregnation-deposition method was adopted to prepare the nano CeO_2/γ-Al2O3 composite supports. The results of XRD showed that there was no CeO_2-Al2O3 mixture or solid solution, indicating that CeO_2 was only loaded on the surface of Al2O3. The CeO_2/γ-Al2O3 composite support had larger specific surface area (170 m2·g-1), while for the non-loaded nanosized CeO_2, the specific surface area was small(～50 m2·g-1). The influence of impregnation and drying methods on the surface properties, thermal stability and crystal structure of composite supports was characterized by XRD, DTA and BET. The CeO_2/γ-Al2O3 composite support prepared by vacuum impregnation and microwave drying was better than that prepared by conventional impregnation and drying.

Hydrothermal Treatment of Sol-Gel TiO_2 Film

The preparation of TiO_2 film has been an important research area.In our work,we obtained the TiO_2 film by hydrothermal treating the amorphous film prepared by sol-gel method or the hydrolysis of titanium alkoxide.The influence of temperature and duration time on the film properties was investigated.The photo degradation of methyl orange in aqueous solution of the film was studied.The films were characterized by XRD and Uv-Vis spectroscope.

Preparation of Nano-Sized TiO_2 Particles by Microemulsion Method

Nano-sized titania powders have been prepared by hydrolysis of tetrabutyl titanate in the droplet of water/OP-7/pentanol/cyclohexane microemulsion system.The effects of ingredient change on the water drop size and particle size were investigated.The prepared TiO_2 was in the form of anatase after annealing.TiO_2 was characterized by TG-TGA, FTIR,XRD to measure the transformation temperature,surface adsorption and average size.

The environmental dependence of different colors in the CMASS sample of the SDSS DR9

I investigate the environmental dependence of galaxy colors in the CMASS sample of the Sloan Digital Sky Survey Data Release 9 （SDSS DR9）. To decrease the radial selection effect, I divide the CMASS sample into subsamples with a redshift binning size of △z = 0.01 and analyze the environmental dependence of the u - r, u - g, g - r, r - i and i - z colors for these subsamples in each redshift bin. Statistical analysis shows that all five colors weakly correlate with the local environment, which may mean that the environmental processes responsible for a galaxy＇s properties pro- ceed slowly over cosmic time.

Application of the Störmer–Verlet-Like Symplectic Method to the Wave Equation

A fourth-order three-stage symplectic integrator similar to the second-order Störmer–Verlet method has been proposed and used before[Chin.Phys.Lett.28(2011)070201;Eur.Phys.J.Plus 126(2011)73].Continuing the work initiated in the publications,we investigate the numerical performance of the integrator applied to a one-dimensional wave equation,which is expressed as a discrete Hamiltonian system with a fourth-order central difference approximation to a second-order partial derivative with respect to the space variable.It is shown that the Störmer–Verlet-like scheme has a larger numerical stable zone than either the Störmer–Verlet method or the fourth-order Forest–Ruth symplectic algorithm,and its numerical errors in the discrete Hamiltonian and numerical solution are also smaller.

Enhanced near-infrared responsivity of silicon photodetector by the impurity photovoltaic effect

The near-infrared responsivity of a silicon photodetector employing the impurity photovoltaic （IPV） effect is investigated with a numerical method. The improvement of the responsivity can reach 0.358 A/W at a wavelength of about 1200 nm, and its corresponding quantum efficiency is 41.1%. The origin of the enhanced responsivity is attributed to the absorption of sub-bandgap photons, which results in the carrier transition from the impurity energy level to the conduction band. The results indicate that the IPV effect may provide a general approach to enhancing the responsivity of photodetectors.

β-FeSi_2 as the bottom absorber of triple-junction thin-film solar cells: A numerical study

Using β-FeSi2 as the bottom absorber of triple-junction thin-film solar cells is investigated by a numerical method for widening the long-wave spectral response. The presented results show that the β-FeSi2 subcell can contribute 0.273 V of open-circuit voltage to the a-Si/μc-Si/β-FeSi2 triple-junction thin-film solar cell. The optimized absorber thicknesses for a- Si, μ-Si, and/3-FeSi2 subcells are 260 nm, 900 nm, and 40 nm, respectively. In addition, the temperature coefficient of the conversion efficiency of the a-Si/μc-Si//3-FeSi2 cell is -0.308 %/K, whose absolute value is only greater than that of the a-Si subcell. This result indicates that the a-Si/μc-Si/β-FeSi2 triple-junction solar cell has a good temperature coefficient. As a result, using β-FeSi2 as the bottom absorber can improve the thin-film solar cell performance, and the a-Si/μc-Si/β-FeSi2 triple-junction solar cell is a promising structure configuration for improving the solar cell efficiency.

A New Class of Scaling Correction Methods

When conventional integrators like Runge-Kutta-type algorithms are used,numerical errors can make an orbit deviate from a hypersurface determined by many constraints,which leads to unreliable numerical solutions.Scaling correction methods are a powerful tool to avoid this.We focus on their applications,and also develop a family of new velocity multiple scaling correction methods where scale factors only act on the related components of the integrated momenta.They can preserve exactly some first integrals of motion in discrete or continuous dynamical systems,so that rapid growth of roundoff or truncation errors is suppressed significantly.

Local Environmental Dependence of Galaxy Properties in a Volume-Limited Sample of Main Galaxies

Using a volume-limited sample of Main Galaxies from SDSS Data Release 5, we investigate the dependence of galaxy properties on local environment. For each galaxy, a local three-dimensional density is calculated. We find that the galaxy morphological type depends strongly on the local environment; galaxies in dense environments have predominantly early type morphologies. Galaxy colors have only a weak dependence on the environment. This puts an important constraint on the process of galaxy formation.

Low Temperature Direct Synthesis of Strontium Titanate Powder

Low temperature direct synthesis (LTDS) involves the preparation of a base solution of Sr^(2+),and the mixing of base solution with tetrabutyl titanate solution.LTDS is an advantageous method because it does not require the complex hydrothermal facilities and it can prevent the agglomeration in calcinations of other liquid methods.In our work,we adopted LTDS method to prepare the nano strontium titanate powders,and characterize them by XRD,FT-IR and TGA.The influences of preparation temperature and solvents on grain size and lattice parameters were investigated.The results show that preparation temperature can slightly change the lattice parameters of grain,while solvents also play important roles in the preparation.

A tool for the morphological classification of galaxies: the concentration index

Using galaxy data from the Sloan Digital Sky Survey Data Release 8, I ex- plore whether the concentration index is a good morphological classification tool and find that a reasonable sample of pure late-type galaxies can be constructed with the choice of the r-band concentration index ci=2.85. The opposite is not true, however, due to the fairly high contamination of an early-type sample by late-type galaxies. In such an analysis, the influence of selection effects is less important. To disentangle correlations of the morphology and concentration index with stellar mass, star forma- tion rate （SFR）, specific star formation rate （SSFR） and active galactic nucleus （AGN） activity, I investigate correlations of the concentration index with these properties at a fixed morphology and correlations of the morphology with these properties at a fixed concentration index. It is found that at a fixed morphology, high-concentration galaxies are preferentially more massive and have a lower SFR and SSFR than low- concentration galaxies, whereas at a fixed concentration index, elliptical galaxies are preferentially more massive and have a lower SFR and SSFR than spiral galaxies. This result shows that the stellar mass, SFR and SSFR of a galaxy are correlated with its concentration index as well as its morphology. In addition, I note that AGNs are pref- erentially found in more concentrated galaxies only in the sample of spiral galaxies.

Comparison of some properties of star forming galaxies and active galactic nuclei between two BOSS galaxy samples from SDSS DR9

Using the LOWZ and CMASS samples of the ninth data release （DR9） from the SDSS-III Baryon Oscillation Spectroscopic Survey （BOSS）, I investigate properties of star forming galaxies and active galactic nuclei （AGNs）. The CMASS sample seriously suffers from the radial selection effect, even within the redshift 0.44 〈 z 〈 0.6, which will likely lead to statistical conclusions in the CMASS sample being less robust. In the LOWZ sample, the fraction of star-forming galaxies is nearly constant from the least dense regime to the densest regime; the AGN fraction is also insensitive to the local environment. In addition, I note that in the LOWZ sample, the distributions of stellar mass and stellar velocity dispersion for star forming galaxies and AGNs are nearly the same.

Two New Fourth-Order Three-Stage Symplectic Integrators

Two new fourth-order three-stage symplectic integrators are specifically designed for a family of Hamiltonian systems,such as the harmonic oscillator,mathematical pendulum and latticeφ4 model.When the nonintegrable latticeφ4 system is taken as a test model,numerical comparisons show that the new methods have a great advantage over the second-order Verlet symplectic integrators in the accuracy of energy,become explicitly better than the usual non-gradient fourth-order seven-stage symplectic integrator of Forest and Ruth,and are almost equivalent to a fourth-order seven-stage force gradient symplectic integrator of Chin.As the most important advantage,the new integrators are convenient for solving the variational equations of many Hamiltonian systems so as to save a great deal of the computational cost when scanning a lot of orbits for chaos.

Photoemission cross section：A critical parameter in the impurity photovoltaic effect

A numerical study has been conducted to explore the role of photoemission cross sections in the impurity photovoltaic（IPV） effect for silicon solar cells doped with indium. The photovoltaic parameters（short-circuit current density, opencircuit voltage, and conversion efficiency） of the IPV solar cell were calculated as functions of variable electron and hole photoemission cross sections. The presented results show that the electron and hole photoemission cross sections play critical roles in the IPV effect. When the electron photoemission cross section is 10^-20cm^2, the conversion efficiencyη of the IPV cell always has a negative gain（△η 0） if the IPV impurity is introduced. A large hole photoemission cross section can adversely impact IPV solar cell performance. The combination of a small hole photoemission cross section and a large electron photoemission cross section can achieve higher conversion efficiency for the IPV solar cell since a large electron photoemission cross section can enhance the necessary electron transition from the impurity level to the conduction band and a small hole photoemission cross section can reduce the needless sub-bandgap absorption. It is concluded that those impurities with small（large） hole photoemission cross section and large（small） electron photoemission cross section,whose energy levels are near the valence（or conduction） band edge, may be suitable for use in IPV solar cells. These results may help in judging whether or not an impurity is appropriate for use in IPV solar cells according to its electron and hole photoemission cross sections.

Nanoscale Ni-B amorphous alloy catalyst supported on carbon nanotubes

Heat treatment of carbon nanotubes(CNTs) was carried out under ammonia atmosphere and then CNTs were modified by Triton x-100(CNTs-T). Ni-B amorphous alloy catalysts supported on CNTs and CNTs-T were prepared by impregnation-chemical reduction method. The catalysts were characterized by TEM,ICP,XRD,BET and CO chemisorption,and studied in the acetylene selective hydrogenation. The results show that homogeneous Ni-B amorphous particles with mean size about 10 nm are successfully prepared on CNTs-T. Compared with Ni-B/CNTs,nickel loading of Ni-B/CNTs-T is increased by about 14.6%. Furthermore,the activity and selectivity of Ni-B/CNTs-T are much higher than those of Ni-B/CNTs in the acetylene selective hydrogenation under comparative condition.

Negative refractive index in a four-level atomic system

A closed four-level system in atomic vapour is proposed, which is made to possess left handedness by using the technique of quantum coherence. The density matrix method is utilized in view of the rotating-wave approximation and the effect of a local field in dense gas. The numerical simulation result shows that the negative permittivity and the negative permeability of the medium can be achieved simultaneously （i.e. the left handedness） in a wider frequency band under appropriate parameter conditions. Furthermore, when analysing the dispersion property of the left-handed material, we can find that the probe beam propagation can be controlled from superluminal to subluminal, or vice versa via changing the detuning of the probe field.

The Existence and Uniqueness for the Solution of Neutral Stochastic Functional Differential Equations with Infinite Delay

In this paper, we will make use of a new method to study the existence and uniqueness for the solution of neutral stochastic functional differential equations with infinite delay （INSFDEs for short） in the phase space BC（（？∞,0];Rd）. By constructing a new iterative scheme, the existence and uniqueness for the solution of INSFDEs can be directly obtained only under uniform Lipschitz condition, linear grown condition and contractive condition. Meanwhile, the moment estimate of the solution and the estimate for the error between the approximate solution and the accurate solution can be both given. Compared with the previous results, our method is partially different from the Picard iterative method and our results can complement the earlier publications in the existing literatures.

STABILIZATION OF SWITCHED LINEAR SYSTEMS WITH CONSTRAINED INPUTS

The stabilization of switched linear systems with constrained inputs （SLSCI） is considered. The authors design admissible linear state feedbacks and the switching rule which has a minimal dwell time （MDT） to stabilized the system. First, for each subsystem with constrained inputs, a stabilizing linear state feedback and an invariant set of the closed-loop system are simultaneously constructed, such that the input constraints are satisfied if and only if the closed-loop system＇s states lie inside this set. Then, by constructing a quadratic Lyapunov function for each closed-loop subsystem, an MDT is deduced and an MDT-based switching strategy is presented to ensure the stability of the switched system.

Distributed heavy-ball algorithm of Nash equilibrium seeking for aggregative games

In this paper,we consider the Nash equilibrium(NE)seeking problem for aggregative games and design a distributed heavy-ball algorithm to solve it.This algorithm has faster convergence rate than the well-known distributed first-order algorithms for aggregative games.In order to seek the NE,each player needs to exchange information with its neighbours as well as a cen-tral aggregation.For aggregative games,the aggregative term can be either linear or nonlinear in this paper.Furthermore,we consider the generalised Nash equilibrium seeking problem for aggregative games by taking into account the linear coupled constraints among players,and modify our initial algorithm to include game constraints.

Mathematical analysis on a multidimensional model of morphogen transport with receptor synthesis

In biological development, morphogens are locally produced and spread to other regions in organs, forming gradients that control the inter-related pattern and growth of developing organs. Mechanisms of morphogen transport were built and investigated by numerical simulations in [A. D. Lander, Q. Nie and F. Y. M. Wan, Do morphogen gradients arise by diffusion？ Developmental Cell 2 （2002） 785-796]. In that paper, model C, which considers endocytosis, exocytosis and receptor synthesis and degradation, is in a one-dimensional spatial region and couples a partial differential equation with ordinary differential equations. Here, this model is promoted to an arbitrary dimension bounded region. We prove existence, uniqueness and non-negativity of a global solution for this advanced model, of its steady-state solution and linear stability of steady state by operator semigroup, the Schauder theorem and local perturbation method. Our results improve previous results for this model in a one dimension region.