Big Bounce Singularity of a Simple Five—Dimensional Cosmological Model

The big bounce singularity of a simple five-dimensional cosmological model is studied.Contrary to the standard big bang space-time singularity,this big bounce singularity is found to be an event horizon at which the scale factor and the mass density of the universe are finite,while the pressure undergoes a sudden transition from negative infinity to positive infinity.By using coordinate transformation it is also shown that before the bounce the universe contracts deflationary.According to the proper-time,the universe may have existed for an infinitely long time.     

Properties of Diamond-Like Carbon Films Synthesized by Dual-Target Unbalanced Magnetron Sputtering

Smooth, dense and uniform diamond-like carbon films (DLC films) for industrial applications have successfully been prepared by dual-target unbalanced magnetron sputtering and the DLC characteristics of the films are confirmed by Raman spectra. It is found that the sputtering current of target plays an important role in the DLC film deposition. Deposition rate of 3.5 μm/h is obtained by using the sputtering current of 30 A. The friction coefficient of the films is 0.2-0.225 measured by using a pin-on-disc microtribometer. The structure of the films tends to have a growth of sp^3 bonds content at high sputtering current. The compressive residual stress in the films increases with the increasing sputtering current of the target.     

丁二烯在含有机镁铝络合物稀土催化剂中的聚合

本文研究定向稀土催化剂组份中引入镁铝络合物后对丁二烯聚合的影响。改变镁铝络合物与氯化物的种类和用量,皆明显的影响其聚合活性。当催化剂中含有苯基镁的烷基铝络合物时,聚丁二烯反-1,4链节可达36%。选择适当的催化剂组成和配比时,含镁稀土定向催化剂具有较高的聚合活性。     

论珠心算教学中的“赏识教育”

在教学中运用"赏识教育",坚持动静结合、以动为主,寓教于乐的教学原则培训儿童,不但能学会珠心算,而且幼儿家长也学会运用"赏识教育"来引导孩子。因此,我认为"赏识教育"是幼儿珠心算教育的灵魂和法宝。     

抓好珠算训练培养优秀人才

我校是一所文理兼备的综合性省属粮食中等专业学校。珠算作为一门计算技术是经济管理类专业的专业基础课。珠算教学质量的高低,直接影响到学生专业课的学习、智能的发展和业务素质。我校从80年代以来,为适应粮食部门实际工作的需要,高水准、严要求地培养计算人才。全校师生普遍重视珠算     

Comparison of Supernovae Datasets Constraints on Dark Energy

Cosmological measurements suggest that our universe contains a dark energy component. In order to study the dark energy evolution, we constrain a parameterized dark energy equation of state ω（z） = ω0 ＋ ω1 1＋z/z using the recent observational datasets： 157 Gold type Ia supernovae and the newly released 182 Gold type Ia supernovae by the maximum likelihood method. It is found that the best fit ω（z） crosses -1 in the past and the present best fit value of ω（0） 〈 -1 obtained from 157 Gold-type Ia supernovae. The crossing of-1 is not realized and ω0 = -1 is not ruled out in 1σ confidence level for the 182 Gold-type Ia supernovae. It is also found that the range of parameter ω0 is wide even in 1σ confidence level and the best fit ω（z） is sensitive to the prior of Ωm.     

Observational constraints on the accelerating universe in the framework of a 5D bounce cosmological model

In the framework of a five-dimensional (5D) bounce cosmological model, a useful function f(z) is obtained by giving a concrete expression of deceleration parameter q(z)=q₁+{q₂}/{1+ln (1+ z)}. Then using the obtained Hubble parameter H(z) according to the function f(z), we constrain the accelerating universe from recent cosmic observations: the 192 ESSENCE SNe Ia and the 9 observational H(z) data. The best fitting values of transition redshift z_T and current deceleration parameter q₀ are given as z_T= 0.65_-0.12^0.25 and q₀ = - 0.76_-0.15^+0.15 (1σ). Furthermore, in the 5D bounce model it can be seen that the evolution of equation of state (EOS) for dark energy w_de can cross over -1 at about z=0.23 and the current value w_0de= - 1.15<- 1. On the other hand, by giving a concrete expression of model-independent EOS of dark energy w_de, in the 5D bounce model we obtain the best fitting values z_T= 0.66_0.08^+0.11 and q₀ = - 0.69_0.10^+0.10 (1σ) from the recently observed data: the 192 ESSENCE SNe Ia, the observational H(z) data, the 3-year Wilkinson Microwave Anisotropy Probe (WMAP), the Sloan Digital Sky Survey (SDSS) baryon acoustic peak and the x-ray gas mass fraction in clusters.     

Statefinder Diagnostic for Phantom Model with V（φ） = Voexp（-λφ^2）

We investigate the phantom field with potential V（φ） = Voexp（-λφ^2） and dark matter in the spatially flat Friedman-Robertson-Walker model It has been shown by numerical calculation that there is a attractor solution in this model We also apply tile statefinder diagnostic to this phantom model. It is shown that tile evolving trajectories of this scenario in tile s - r diagram is quite different from other dark energy models.     

Cosmological Constant or Variable Dark Energy？

Selection statics of the Akaike information criterion （AIC） model and the Bayesian information criterion （BIC） model are applied to the A-cold dark matter （ACDM） cosmological model, the constant equation of state of dark energy, w =constant, and the parametrized equation of state of dark energy, w（z） = wo ＋ wlz/（1 ＋ z）, to determine which one is the better cosmological model to describe the evolution of the universe by combining the recent cosmic observational data including She Ia, the size of baryonic acoustic oscillation （BAO） peak from SDSS, the three-year WMAP CMB shift parameter. The results show that AIC, BIC and current datasets are not powerful enough to discriminate one model from the others, though odds suggest differences between them.     

氮掺杂碳纳米管的合成及活化过一硫酸盐的性能与机理

以多壁碳纳米管(MWCNT)为原材料, 三聚氰胺为氮前体, 采用高温煅烧法制得了含氮量约3.33%(摩尔分数)的氮掺杂碳纳米管(N-CNT-700), 该纳米管为一维材料. N-CNT-700活化过一硫酸盐(PMS)体系60 min内对苯酚的降解效率可达100%, 总有机碳(TOC)去除率可达61.6%, 体系的活化能为35.4 kJ/mol. 通过电子顺磁共振(EPR)检测、 掩蔽实验及PMS浓度测定等方式确定了体系降解机制为自由基(·OH, SO₄^·-)与非自由基共同作用, 除去9%的吸附去除外, 91%的氧化降解中自由基作用占比约49%, 单线态氧(¹O₂)作用占比约18%, 活性中间体作用占比约24%. N-CNT-700的反应活性随着重复利用次数的增加而降低, 高温处理可以恢复其高反应活性. 煅烧温度影响材料中的氮含量及种类, N-CNT的反应活性与氮含量成正比, 且与石墨氮含量密切相关.