高红移Lyman Break星系

总结了到目前为止用所谓 Lyman Break方法(亦称为UV drop 方法)观测得到的高红移(z≈3)Lyman break星系的观测特征,包括光度函数、半光度半径分布、空间密度及成团性、恒星速度弥散、超星风及大尺度气体团块运动和金属丰度等。还对其目前的理论工作做了综合介绍,对当前两种主要模型进行了评述并提出了作者的个人观点。

First principles study on electronic structure and optical properties of novel Na-hP4 high pressure phase

The electronic structure and optical properties of novel Na-hP4 high pressure phase at different pressures(260,320,400 and 600 GPa)were investigated by the density functional theory(DFT)with the generalized gradient approximation(GGA)for the exchange and correlation energy.The band structure along the higher symmetry axes in the Brillouin zone,the density of states(DOS) and the partial density of states(PDOS)were presented.The band gap increases and the energy band expands to some extent with the pressure increasing.The dielectric function,reflectivity,energy-loss function,optical absorption coefficient,optical conductivity, refractive index and extinction coefficient were calculated for discussing the optical properties of Na-hP4 high pressure phase at different pressures.

Photoabsorption Spectra of Si_n and Si_nO (n ≤ 5)

The photoabsorption spectra have been calculated for Sis and SilO （n ≤ 5） clusters using time-dependent density-function theory. Our studies suggest that Sin-1 O clusters are relatively stable than those of corresponding Sis clusters. Moreover, substantial differences are observed among the absorption spectra of different molecules in the energy region （0 - 8 eV）. Comparing two different exchange-correlation potentials, local-density and generalized-gradient approximations, both calculated optical spectra present the same spectral feature.

Large eddy simulation of a round jet into a counterflow

A round jet into a counterflow under different jet-to-current velocity ratios was investigated using large eddy simulation.The results agree well with experimental measurements from laser-Doppler anemometry and laser-induced fluorescence that include velocity and mean concentrations along the centerline and radial direction.Vortex rings appear in the region near the jet exit and large-scale vortex structures still occur near the stagnation point.The flow becomes more chaotic and three-dimensional with the presence of these structures.In particular,their presence near the stagnation point results in large velocity fluctuations that enhance the mixing process and dilution.These fluctuations are described by probability density functions that deviate from Gaussian distribution.The three-dimensional streamlines indicate that the jet not only oscillates in three directions but also rotates about the jet axis and around the vortex.The second and third moments of the velocity or scalar fluctuations identify that the mixing processes are greater in the region before the stagnation point.

First-principles calculations of optical properties of Mg_2Pb

Based on the density functional theory （DFT）, the electronic structures and optical properties of Mg2Pb are calculated by using the local density approximation （LDA） and plane wave pseudo-potential method. The calculation results show that the indirect band gap width of Mg2Pb is 0.02796 eV. The optical properties of MgzPb have isotropic characteristics, the static dielectric function of Mg2Pb is ε1（0） = 10.33 and the refractive index is n0 = 3.5075. The maximum absorption coefficient is 4.8060×10^5 cm-1. The absorption in the photon energy range of 25-40 eV approaches to zero, shows the optical colorless and transparent behaviors.

Supersmooth density estimations over L^p risk by wavelets

This paper studies wavelet estimations for supersmooth density functions with additive noises. We first show lower bounds of Lprisk(1 p < ∞) with both moderately and severely ill-posed noises. Then a Shannon wavelet estimator provides optimal or nearly-optimal estimations over Lprisks for p 2, and a nearly-optimal result for 1 < p < 2 under both noises. In the nearly-optimal cases, the ratios of upper and lower bounds are determined. When p = 1, we give a nearly-optimal estimation with moderately ill-posed noise by using the Meyer wavelet. Finally, the practical estimators are considered. Our results are motivated by the work of Pensky and Vidakovic(1999), Butucea and Tsybakov(2008), Comte et al.(2006), Lacour(2006) and Lounici and Nickl(2011).